JPS62142809A - Speed control device for steam turbine - Google Patents

Abstract

PURPOSE:To aim at the improvement of the rate of operation in a plant by causing a control unit to limit the opening of a steam governing valve so that it is kept almost constant within the limits of the practicable uninterrupted operation of an nuclear reactor when a speed request signal remains within the range of values corresponding to a prescribed governing valve opening request signal. CONSTITUTION:A speed setting signal 25a from a speed setting device 25 is compared with an actual speed signal from a steam turbine by means of an adder 26, and the deviation signal 26a is output to a turbine speed governor 27. Hereupon, a correction is made by applying a permanent speed variation so that approximately five percent of the variation in the deviation signals 26a correspond to hundred percent of the variation in load preset values, and then, the output signal 27a thereof is added to a load setting signal 29a from a load setting device 29 so as to make a speed request signal 28a, which is output to an output limiting device 30. And further, a corrected speed request signal 30a, which is obtained from placing a limitation on the signal 28a according to the variation in the deviation signals 26a, is output as an operation signal, and then, by comparing the operation signal with a pressure request signal 32a from a pressure control device 32, either of the two signals, whichever has a lower value, is output as a governing valve opening request signal 31a.

Description

[Detailed description of the invention] [Technical field of invention] TECHNICAL FIELD This invention relates to steam turbine speed control systems.

[Technical background of the invention and its problems]

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, in the event of a breakdown such as a transmission line accident 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 user will be 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 steam flow to 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 a nuclear reactor is not preferable for a boiling water reactor because it causes a fluctuation in the reactor output. In particular, if the pressure increases, the reactor output increases, and if it exceeds a limit value, the operation of the nuclear reactor will be automatically stopped, and the operation of the power plant will be shut down.

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.

In other words, FIG. 6 is a schematic system diagram of a nuclear turbine plant, in which steam generated in the nuclear reactor 11 is passed through the main steam conduit 1.
2, the steam is guided to the steam turbine 14 while its flow rate is controlled by the steam control valve 13, and is subjected to rotation of the steam turbine 14. Then, the power generation 115 directly connected to the steam turbine 14 is driven, and the power generated there is sent to the power system via the 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 conduit 12, and a part of the main steam is transferred to the steam turbine 1 as necessary.
4 is bypassed and led to the condenser 17.

On the other hand, a frequency detector 20 for measuring the power system frequency is provided at the exit 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 adds the output signal 21a to tH5!
Issued on the 22nd. 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 set value of this load setter 23 has the purpose of removing disturbances to Plan 1- due to minute changes in the system frequency, and is normally set to a value 10% higher than the required load set value. This additional amount is called load setting bias. Further, the opening degree of the steam control valve 13 is controlled by a steam turbine speed Lll1g device so that the deviation between the actual turbine speed and the set speed is within a certain range, and the steam inflow 1 of the steam turbine 14 is adjusted. Furthermore, in response to the control of the opening direction of the steam control valve 13, the bypass valve 18 is controlled in the opening direction, and excess steam is guided to the condenser 17.

However, generally the steam volume M that can flow through the bypass valve 18 is
It is about 25% of the capacity of the steam control valve 13. Therefore, when the frequency of the power system greatly increases and the opening degree of the steam regulating valve 13 is significantly reduced in order to prevent the upper limit of the rotation speed, the opening degree of the steam regulating valve 13 is reduced within 25%. If so, excess steam can be absorbed by the bypass valve 18 having a capacity of 25%, thereby preventing a rise in reactor pressure. but,
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 to 8 or more points of the bypass valve 18, causing an increase in reactor pressure.
There are problems such as the reactor 11 automatically stopping due to an increase in the reactor output.

The restriction of the steam control valve 13 when the frequency increases is determined by the speed adjustment rate applied to the steam turbine speed control device, and currently the speed adjustment m is set at 5%. That is,
When the actual turbine speed increases by 5%, the steam control valve 13
00%, and a 5% increase in the actual turbine speed is converted to 52.5Hz when converted to 50Hz. FIG. 7 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 the frequency that can be absorbed by the bypass valve 18 is determined, the above-mentioned load setting bias 10 %, it becomes 50.875Hz.

On the other hand, it is generally necessary to consider a frequency increase of up to 1.5 Hz in the event of a power system failure.

Therefore, the current capacity of the bypass valve 18 is insufficient, but increasing the capacity of the bypass valve 18 would require a significant increase in equipment, which would increase plant construction costs and is not realistic.

[Purpose of the invention]

The present invention was made in consideration of such boiling,
While using the current bypass valve, by setting a certain opening limit for the regulating valve opening request signal of the reactor power control device, the reactor can be operated even if the frequency of the power system rises to about 51.511z. An object of the present invention is to provide a steam turbine speed control device that allows continuous operation without stopping the steam turbine.

[Summary of the invention]

The steam turbine control device of the present invention includes a turbine governor that corrects a change in an input turbine speed deviation signal in relation to a load setting value and outputs the corrected change as a turbine governor output signal;
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 the content of the speed request signal can be absorbed by the capacity of the bypass valve. When the value is within the range between the value corresponding to the master steam moderation valve opening request signal and the value corresponding to the steam moderation valve opening request signal that is larger by a fixed m than that value, the opening of the steam moderation valve is set to The device is characterized by being formed with an output limiter that outputs an operating signal that is kept almost constant within a range where continuous operation is possible, and over the range, the steam control valve is throttled while the bypass valve is fully open. This is to prevent unnecessary plant shutdowns.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

1 to 4 show one embodiment of the present invention, and FIG. 1 is an overall block diagram.

In FIG. 1, reference numeral 25 is a speed setter, which 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 governor 27 is configured such that a 5% change in the turbine speed deviation signal 26a causes a 1% change in the load setting value.
The adder 28 corrects it with a speed regulation rate that corresponds to a change of 00% and outputs it as the turbine governor output signal 27a.
It is configured to be output to. This adder 28 receives the turbine governor output signal 27a and the load setting? 529 load setting signal 29a and output to the output limiter 30 as the speed request signal 28a. A turbine speed deviation signal 26a is inputted to the output limiter 30 as a signal for setting a limiting condition, and a limit is applied to the speed request signal 28a according to a change in the turbine speed deviation signal 26a, that is, a change in the system frequency. The corrected speed request signal 30a is output to the output limiter 3 as an operation signal.
It is configured to be output from 0. This correction speed request signal 30a is input to a 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 this low value P1 pre-circuit 31. This low 11i 11 ahead circuit 3
1 is configured to output the lower value signal of the two signals 3Qa and 32a as a control valve opening request signal 31a for the steam control valve 13.

The opening degree of the steam control valve 13 is controlled by this signal 31a. Further, the pressure request signal 32a output from the pressure controller 32 is also applied to the caulking device 33. This Q adder 33 compares the pressure request signal 32a and the regulating valve request signal 31a, and converts the difference signal into the bypass valve opening request signal 33.
It is formed so as to be output as a. The opening degree of the bypass valve 18 is controlled by this bypass valve opening degree request signal 33a.

The output limiter 30 is given characteristics as shown in FIG. 2, and its operation is as follows.

That is, first, the frequency deviation is -2.5Hz to ±OHZ.
In other words, while the turbine speed deviation signal 26a is between +5% and O%, which is the limiting condition for the output limiter 30,
The value of the correction speed request signal 30a of the output limiter 30 is 100.
% is held constant.

As a result, the steam control valve 13 and the bypass valve 18 remain unchanged in their rated operating conditions.

Next, the frequency deviation is ±OI-1z~+0.8751-I
Z (see FIG. 3), that is, the turbine speed deviation signal 26a, which is the limiting condition for the output limiter 30, is between 0% and -1.
, 75%, the value of the corrected speed request signal 30a of the output limiter 30 changes linearly from 100% to 75%. Therefore, until the upper limit deviation of the system frequency reaches +0.875Hz, the speed regulation rate of the turbine governor 27 (5% deviation to 100% of the load setting value) is adjusted according to the upper limit deviation of the system frequency.
), the steam control valve 13 is narrowed down,
At the same time, the bypass valve 18 is opened by the amount by which the steam control valve 13 is throttled. This frequency deviation +0.875 Hz becomes 25% when converted to the opening degree of the bypass valve 18. This value is obtained as follows. In other words, the frequency deviation of 0.875Hz is equal to the steady setting frequency of 501-(1 of z).
．． 75%, which corresponds to 35% of the load setting value when converted to the load setting value using the speed adjustment rate, but the normal load setting value has a +10% load setting bias as mentioned above. Since it has been added, subtracting this value will set the load! This corresponds to 25%. As a result, the frequency deviation +0.875Hz becomes 75% as the steam regulating valve opening request, and the opening degree request to the bypass valve 18 is equal to the steam regulating valve opening request value of 100% during rated operation and the steam regulating valve opening request. A request for 25% opening will be issued, which is a difference from the required opening of 75%.

Furthermore, between the frequency deviation +0.875 Hz and +1.5 Hz, that is, while the turbine speed deviation signal 26a, which is the limiting condition for the output limiter 30, is between -1.75% and -3%,
The value of the correction speed request signal 30a of the output limiter 30 is 75.
% is held constant.

Therefore, during this period, the steam control valve 13 and the bypass valve 18
Both are maintained at the above-mentioned frequency deviation of +0.875 Hz.

Finally, while the frequency deviation is -4 between +1.5Hz and +2.5l-1z, while the turbine speed deviation signal 26a, which is the limiting condition for the output limiter 30, is between -3% and -5%, the output is The value of the correction speed request signal 30a of the limiter 3o is 7.
It changes linearly from 5% to 0%. Therefore, the steam control valve 13 is further narrowed down from 75% opening due to the frequency deviation, but since the upper limit of the discharge capacity of the bypass valve 18 is 25%, excess steam can be discharged and the reactor pressure increases, which causes the plant to shut down when the neutron flux reaches the scram set point.

FIG. 4 is an explanatory diagram of the transient response of the steam control valve, etc. when the system frequency increases in the device of the present invention, and FIG.
shows the frequency of the power system, (b) shows the opening degrees of the steam control valve and the bypass valve, and (C) shows the respective temporal changes in the reactor output.

As shown in FIG. 4(a), the frequency is set to 5.
It rises from 0Hz to 51.5Hz in 2 seconds, and 5 in 3 seconds.
If the frequency is maintained at 1.5 Hz and further increases after 5 seconds, the actual turbine speed increases as the frequency increases, the speed request signal 28a becomes smaller, and the pressure request signal 3
2a remains almost constant at 100%, the speed request signal 28a becomes the adjustment valve opening request signal 31a through the low value priority circuit 31, and the steam adjustment valve gradually changes as shown in FIG. 4(b). It closes on. And the frequency is 50.875
When the temperature reaches Hz, the steam control valve 13 is in a state where it is throttled down by 25%. On the contrary, the bypass valve 18 opens in response to the narrowing of the steam regulating valve 13, and since the capacity of the bypass valve 18 is 25% of the capacity of the steam regulating valve 13, when the steam regulating valve 13 is throttled by 25%, It will be fully opened.

Therefore, when the frequency further increases, in the conventional device, the steam control valve 13 as shown by the dotted line in FIG.
is further narrowed down, and since the bypass valve 18 is already fully open, the reactor output increases as shown by the dotted line in Fig. 4(C), and eventually exceeds the scram set value.
The reactor 11 comes to automatic shutdown.

However, in the present invention, since the output limiter 30 having the characteristics as shown in FIG. The system will remain open at 75% and wait for the power grid frequency to return to 50Hz. That is, within this period, normally the recirculation pump 2
4 is exerted, the increase in the output of the reactor 11 is suppressed, and the increase in frequency is contained within a few seconds, so the reactor 11 is prevented from automatically stopping.

In addition, in the event that the frequency further increases after 5 seconds as shown in FIG. 4(a), the steam control valve 13
is operated in the opening direction, the reactor output increases and the reactor 11 automatically stops as shown in FIG. 4(C).

However, this is a case where the system stabilization device installed to suppress a significant increase in system frequency does not operate normally, and it is unavoidable that the nuclear reactor 11 will stop.

FIG. 5 is a block diagram showing another embodiment of the invention.

In the example of Kinoto, the configuration is the same as above until the speed request signal 28a is obtained by adding the turbine governor force signal 27a and the load setting signal 29a of the load setting device 29 with the addition/subtraction 328. It is structured as follows. That is, the positions of the output limiter 30 and the low value priority circuit 31 are exchanged, and the input signal to the output limiter 30 is formed as the adjustment valve opening request signal 31a of the low value priority circuit 31. Therefore, the speed request signal 28a is input to the low 11 speed priority circuit 31. This low value priority circuit 31 includes a pressure controller 32 for controlling the pressure of the nuclear reactor 11 at a constant level.
A pressure request signal 32a output from is also input,
Here, the low value signal of the two signals 28a and 32a is the control valve opening request signal j%31a for the steam control valve 13.
This control valve opening request signal 31a is input to the output limiter 30. This output limiter 30 includes:
Turbine speed deviation signal 2 is used as a signal for setting limit conditions.
63 is input. This turbine speed deviation signal 26
According to a change in a, that is, a change in the system frequency, a limit is applied to the adjustment valve opening request signal 31a, and an operation signal consisting of a corrected adjustment valve opening request signal 30 is output from the output limiter 30, and this signal 30b The opening degree of the steam control valve 13 is controlled.

On the other hand, the pressure request signal 32 output from the pressure controller 32
a is also applied to the booster 33, where it is compared with the control valve request signal 31a, and the deviation signal is output as the bypass valve opening request signal 33a. The opening degree is controlled.

The characteristics of this output limiter 30 are exactly the same as those of the previous embodiment, and its operation is also similar.

The difference between the above embodiment and this embodiment is that the setting position of the output limiter 30 is different. In the case of the above embodiment, the opening degree is limited by the output limiter 30 in response to the opening degree request signal for both the steam control valve 13 and the bypass valve 18, but in the case of this embodiment, the opening degree is limited by the output limiter 30. The temperature limit is applied only to the steam control valve 13. However, in this embodiment, in J3, the bypass valve opening is at the maximum opening, so the operation of the steam turbine 14 can be controlled in the same manner as in the previous embodiment without particularly setting an opening limit. I can do it.

In the embodiment shown in FIG. 5, in order to control the opening and closing of the bypass valve 18 by the output limiter 30,
One input signal may be replaced with the adjustment valve opening request signal 31a of the low value priority circuit 31 and may be the corrected adjustment valve opening request signal 30b of the output limiter 30.

Further, since the output limiter 30 in each of the embodiments described above operates only when the system frequency fluctuates, normal operation can be performed properly as in the conventional case.

[Effect of idea]

Since the steam turbine speed control device of the present invention is configured and operates in this way, even when the frequency of the power system increases, even in a steam turbine plant having a bypass valve of 25% capacity, it can be controlled within the range that can be absorbed by the capacity of the bypass valve. This prevents the plant from immediately shutting down in response to a frequency rise that exceeds the limit, and the frequency rise that occurs in a normal power system when an accident occurs will not cause a plant stoppage, and the frequency will not stop when the bypass valve is fully open. While maintaining recovery, the plant can be operated continuously, and the plant operation rate can be improved.

[Brief explanation of drawings]

1 to 4 show one embodiment of the steam turbine speed control device of the present invention, FIG. 1 is a block diagram showing the whole, FIG. 2 is a diagram showing the characteristics of the output limiter, and FIG. 3 is a diagram showing the characteristics of the output limiter. A diagram showing the relationship between frequency change and adjustment valve opening in this actual flow example, Figure 4 (a)
, (b), and (c) are diagrams showing temporal changes in the frequency, the opening degree of the control valve and the bypass valve, and the output of the reactor, respectively, when the frequency increases, and FIG. 5 shows another embodiment of the present invention. FIG. 6 is a system diagram of a nuclear power turbine plant, and FIG. 7 is a diagram showing the relationship between frequency change and steam control valve opening in a conventional steam turbine speed control device. 13...Steam control valve, 14...Steam turbine, 18
... Bypass valve, 26a... Turbine speed deviation signal, 27... Turbine speed governor, 27a... Turbine speed governor power signal, 28... Adder, 28a... Speed request signal, 29a... Load setting signal, 30... Output limiter, 30a... Correction speed request signal (operating signal), 3
0b...Corrected adjustment valve opening request signal (operation signal), 31
...Low value priority circuit, 31a...Representative of the applicant for the adjustment valve opening request Sato-Yu Output (Z) in Fig. 1 to 5 (Z) Fig. 2 Frequency (Hz) Fig. 3 Time (seconds) Time (Seconds) Time (Seconds) Figure 4 Figure 5 Figure 6 Frequency (Hz) Figure 7

Claims (1)

[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 setting that outputs a load setting signal. an adder for determining the deviation between the turbine governor output signal and the load setting signal and outputting a speed request signal; If the value is within the range between the value corresponding to the steam control valve opening request signal and the value corresponding to the steam control valve opening request signal that is a certain amount larger than that value, the opening of the steam control valve is within the range that allows continuous operation of the reactor. a steam turbine speed control device having an output limiter that outputs an operating signal whose content is maintained substantially constant at . 2. The steam turbine speed control device according to claim 1, wherein the speed request signal is directly input to the output limiter. 3. The steam turbine speed according to claim 1, wherein the speed request signal is input to a low value priority circuit, converted into a control valve opening request signal, and then input to an output limiter. Control device. 4. When the frequency setting value of the output limiter is 50Hz,
The steam turbine according to claim 1, wherein the steam turbine outputs an operating signal that maintains the opening degree of the steam control valve constant when the frequency increase is within the range of 0.875 to 1.5 Hz. Speed control device. 5. The steam turbine speed control device according to claim 1, wherein the output limiter uses a turbine speed deviation signal as a limiting condition.