JPS63302107A - Control device for steam turbine - Google Patents

Abstract

PURPOSE:To enable a turbine to be operated stably by providing a closing speed control means for a turbine bypass valve control system in order to accomplish the closing speed meeting with the opening speed of a steam governor controlled by a steam governor valve control system. CONSTITUTION:The subject device selects a low value signal, as a flow rate requiring signal 13 of a steam governor by means of a low value priority circuit 12, out of both the output signal 10h from a speed control circuit 10 and the output signal 11h from a pressure control circuit 11 so as to control each steam governor 4 (4a through 4d) depending on the aforesaid requiring signal 13. In this case, an adder 31 is provided wherein function generators 30a through 30d estimating the flow rate passing through a valve by inputting the output signal from position detectors 20a through 20d for each steam governor 4, is added to each estimated steam flow rate so as to find out a signal 32 for the total steam flow rate actually passing through the valve. And it is so constituted that the signal of a low value out of each signal 13 and 32 is selected by a low value priority circuit 33 so as to be added to the system of signals 13 required to be used for a turbine bypass valve 9.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention is a steam turbine control device for controlling a steam turbine equipped with a turbine bypass system, and particularly a steam turbine control device suitable for application to a nuclear power generation cycle. The present invention relates to a turbine control device.

(Prior art) A typical configuration example of a steam system in a nuclear power plant is shown in the fifth example.
As shown in the figure. In the system configuration shown in FIG. 5, steam generated in the reactor 1 flows into the steam turbine 5 via the main steam pipe 2, the main steam stop valve 3, and the steam control valve 4 to do work, and the remaining steam is The energy is recovered by the condenser 6. A generator 7 is connected to the steam turbine 5 . The generator 7 is connected to a power system (not shown). On the other hand, in addition to the main steam system described above, a turbine bypass system is installed to absorb excess steam during startup of the reactor 1 or sudden load changes in the steam turbine 5, so that the reactor 1 can continue stable operation. A turbine bypass system 8 having a valve 9 is arranged to bypass the main steam stop valve 3, the steam control valve 4 and the steam turbine 5.

A nuclear power plant having such a configuration is basically operated by main steam pressure control. For example, when the output of the nuclear reactor 1 increases, the main steam pressure increases due to the increase in generated steam, but since the steam control valve 4 increases its opening degree to capture this pressure increase, the steam flow rate to the steam turbine 5 also increases. As a result, the turbine output increases. Turbine bypass valve 9
controls the main steam pressure in cooperation with the steam regulator valve 4. During normal operation, the main steam pressure is controlled by the steam regulator valve 4, so the fully closed position is maintained. When stopped or when the steam control valve 4 is suddenly closed, it is opened to form a turbine bypass system and control the main steam pressure.

The steam control valve 4 is connected to a speed control circuit l as shown in FIG.
The lower value signal obtained by the low value priority circuit (LVG) 12 from the speed control system output signal 10h from the pressure control circuit 11 and the pressure control system output signal 11h from the pressure control circuit 11 is used as the steam control valve flow rate request signal. 13. The turbine bypass valve 9 is controlled based on a signal of the deviation between the pressure control system output signal 11h from the pressure control circuit 11 and the speed control system output signal 10h from the speed control circuit 10. The speed control circuit 10 uses an adder 10c to obtain a deviation between the speed reference set by the speed setter 10a and the actual speed detected by the speed detector 10b, and sends a signal of the deviation to a PI calculator (KS) 10d. PI is calculated, and the sum of this and the load setting signal 10e is obtained by an adder 10f to form a speed control system output signal 10h. On the other hand, the pressure control circuit 11 uses an adder 11C to obtain a deviation between the main steam pressure reference set by the pressure setting device 11a and the main steam pressure detected by the steam pressure detector 11b, and generates a signal of the deviation. A PI calculator (KP) lld performs a PI calculation to form a pressure control system output signal 11h.

The load setting signal 10e is the sum of the steam control valve flow rate request signal 13 and the bias value a set by the bias setting device 10g. This value is higher than the pressure control system output signal 11h. In other words, speed control circuit 1
Speed control system output signal 10h from 0 and pressure control circuit 11
When comparing the pressure control system output signal 11h during normal operation, the latter pressure control system output signal 11h is a low value, and this pressure control system output signal 11h is the output signal of the low value priority circuit 12, that is, the steam control valve. This becomes a flow rate request signal 13.

The purpose of adding the bias value α is to prevent fluctuations in the system frequency etc. from causing disturbance to the reactor 1 during normal operation, and to use this value to set the load setting signal 10.
The objective is to automatically follow e.

The steam regulator flow rate request signal 13 is sent to each steam regulator valve 4 via the steam regulator flow rate request-valve lift correction circuit 14a to 14d.
The valve opening request signals a to 4d are converted into valve opening request signals 15a to 15d, and based on these valve opening request signals, the openings of the steam control valves 4a to 4d are controlled by position control circuits 40a to 40d having the following configuration. Although FIG. 5 typically shows only one steam control valve 4, in reality, steam is supplied to the steam turbine 5 from several locations on its circumference, as shown in FIG. For example, four steam control valves 4a to 4d are provided. Correspondingly, four sets of position control circuits are also provided. Each position control circuit 40a to 40d
have the same configuration, and each has an amplifier 16.
, a limiter 17, a servo valve 18, a servo motor 19, and a position detector 20 for feedback of valve position signals.

The limiter 17 is provided according to the characteristics of steam control and recovery. In other words, in the case of a steam control valve, the operation in the closing direction is performed by the action of a spring installed in the oil cylinder by releasing the hydraulic pressure, so there is no restriction on the closing direction, but in the opening direction, the operation requires a large amount of manipulation. Since oil is required, the speed is generally limited so as not to exceed the capacity of the oil supply system, and the limiter 17 is provided for this speed limit.

On the other hand, the opening request signal 21 to the turbine bypass valve 9 is
Pressure control system output signal 11h and steam control valve flow rate request signal 1
However, during normal operation, these signal levels are equal and are therefore "0", and the turbine bypass valve 9 remains fully open. For some reason, a difference occurs between the two signal levels, and when the signal 11h>signal 13, the opening request signal 21>0 becomes 0, and the turbine bypass valve 9 is driven in the opening direction.

Note that the position control circuit 41 for controlling the opening and closing of the turbine bypass valve 9 is also configured in substantially the same manner as the position control circuit for controlling the steam control valve. It has become.

However, the limiter 1 installed in the case of a steam control valve
A limiter corresponding to 7 is not provided. That is,
In the case of the turbine bypass valve 9, there is no need to provide a limiter because its drive system is generally equipped with an oil supply means, such as an accumulator, capable of supplying a large amount of operating oil.

The operation of the steam turbine control device shown in FIG. 6 having the above configuration will be explained with reference to FIG. 7.

The behavior of each part of the device when the generator frequency, that is, the actual turbine speed increases for some reason while the generator 7 currently connected to the steam turbine 5 is connected to the power grid and is operating at the rated output state. Let's think about it. As shown in FIG. 7, the steam turbine 5 is in the rated output operating state at time TO, and the actual turbine speed detected by the speed detector 10b is equal to the rated speed reference set by the speed setter 10a. shall be taken as a thing. At this time, when comparing the levels of the speed control system output signal 10h and the pressure control system output signal 11h, the bias value α
Because the latter output signal 11h becomes a low value due to the action of
This output signal 11h passes through the low value priority circuit 12 and becomes the steam control valve flow rate request signal 13, and the addition of the bias value α to this value becomes the load setting signal 10e.
A speed control system output signal 10h is formed.

The steam control valve flow rate request signal 13 becomes valve opening request signals 15a to 15d via the steam control valve flow rate request-valve lift correction circuits 14a to 14d, and further outputs to the position control circuits 40a to 4.
The opening degrees of the steam control valves 4a to 4d are determined via 0d.

At this point, the opening request signal 21 to the turbine bypass valve 9 is zero because the output signal 11h of the pressure control circuit 11 and the steam control valve flow rate request signal 13 are equal, and the turbine bypass valve 9 also maintains the fully open position. ing.

Assuming that the system frequency, that is, the actual turbine speed 10b, starts to increase at a constant rate at time T1 from this state, the speed control system output signal 10h gradually decreases, and at time T2, the pressure control system output signal 11h increases. is equal to The only element that changes between time T1 and T2 is the speed control system output signal 10h because the pressure control system output signal 11h has a low value, but after time T2, the value becomes lower than the pressure control system output signal 11h. , this speed control system output signal 10h becomes the steam control valve flow ffi request signal 13. Therefore, time T2
Thereafter, when the speed further increases, the steam control valve 4 starts to close as shown in the figure, while the pressure control system output signal 11h
is almost a constant value, while the steam control valve flow rate request signal 13 decreases, so the turbine bypass valve opening request signal 21 controls the turbine bypass valve 9 in the opening direction with an output signal equal to the difference between the two. become. During this period, the steam control valve 4 and the turbine bypass valve 9 have no limiting elements in the control circuit, so they both have good followability to changes in the output signal level from the speed control circuit 10, and therefore there is little variation in main steam pressure. .

This increase in system frequency stops at time T3 due to load adjustment at each power plant, and at time T4, the turbine speed begins to decrease in an attempt to return to the rated frequency. At this time, changes in the speed control system output signal 10h and the steam regulator flow rate request signal 13 move in the opposite direction to those when the speed increases and follow the changes in the actual speed, but the steam regulator valve 4 changes in the steam regulator flow rate request signal 13. It is not possible to follow the change in the valve opening direction (change in the valve opening direction), and as shown in FIG. 7, the valve opens relatively slowly. This slow movement in the opening direction is controlled by limiters 17a to 17 provided in the position control system of the steam control valve 4.
This is due to the action of d. As a general operation, when the steam control valve 4 moves in the opening direction, a large amount of oil is required as a driving source, so this is restricted and the health of the oil supply system for controlling the steam turbine is maintained. ensure sex.

On the other hand, the turbine bypass valve opening request signal 21 is
It is determined only by the difference between the steam control valve flow rate request signal 13 and the output signal 11h of the speed control circuit 10, and the turbine bypass system 8 is equipped with a closing direction speed limiter as explained in the case of the steam control valve 4 above. Since it is not provided, the movement has good followability, and the turbine bypass valve 9 begins to close at the same time as the speed decreases at time T4, and becomes fully open at time T5 when the actual speed returns to the rated speed.

(Problem to be Solved by the Invention) Between times 14 and 15, a time difference occurs between the steam regulator flow rate request signal 13 to the steam regulator valve 4 and the actual opening degree, and the steam turbine 5 While the amount of steam flowing into the side is restricted, the turbine bypass valve 9 side operates as if generated steam is flowing into the steam turbine 5 side, resulting in an imbalance in the amount of steam between the two sides. will occur.

For this reason, around time T5, the main steam pressure begins to rise rapidly due to surplus steam, which is a very dangerous situation for the reactor 1 side as the nuclear reaction is accelerated, and in some cases, the reactor 1 may be damaged. It may even be necessary to force a scrum. Even if this is not necessary, fluctuations in main steam pressure and unnecessary opening/closing operations of the turbine bypass valve 9 will occur, resulting in a large disturbance in plant operation.

Frequency fluctuations that cause the above problems do not occur very often, but when they occur due to system accidents, the control equipment that should normally act in the direction that suppresses the fluctuations may be forced to operate the reactor. On the contrary, it would be unfavorable for system operation if it caused a scram or otherwise promoted fluctuations.

In order to solve this problem, it is possible to remove the limiters 17a to 17d provided in the position control system of the steam control valve 4, but removing the limiters 17a to 17d would reduce the capacity of the oil supply system. This would require a significant increase, and considering that the frequency of system accidents that cause problems is extremely low, it is not economically advisable.

The present invention has been made in consideration of the above points, and it is possible to stabilize the main steam pressure even when the steam control valve is controlled in the open direction during sudden system frequency fluctuations, thereby improving the turbine performance of the turbine with excellent operating characteristics. It is an object of the present invention to provide a steam turbine control device that can realize operation.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention achieves, in a turbine bypass valve control system, a closing speed that matches the opening speed of the steam regulating valve controlled by the steam regulating valve control system. The invention is characterized in that it is provided with circuit means for doing so.

(Function) According to the above configuration, even if there is a fluctuation in the actual turbine speed, the turbine bypass valve opens and closes at a closing speed that matches the opening speed of the steam control valve that controls the amount of steam supplied to the steam turbine. , it is possible to eliminate load fluctuations seen from the steam generation source side, stabilize the main steam pressure, eliminate harmful effects that promote fluctuations in turbine speed, and realize stable turbine operation.

(Example) A first example of the present invention is shown in FIG. This embodiment is based on the device shown in FIG. 6 and has some additional components added thereto. Components having the same functions as those in FIG. 6 are given the same reference numerals, and their individual Repeated explanation of the constituent elements will be omitted. That is, the device shown in FIG. 1 is based on the device shown in FIG.
A valve lift that uses the output signals of the position detectors 20a to 20d for ~4d as input and predicts the corresponding valve-passing steam flow rate.
Steam flow rate correction circuits 30a to 30d, an adder 31 that adds each steam flow rate predicted by these valve lift-steam flow rate correction circuits 30a to 30d to obtain a total actual valve passing steam flow rate 32, and a steam control valve flow rate. A low value priority circuit 33 which inputs the request signal 13 and the total actual valve passing steam flow rate 32 and outputs the lower value signal of both is connected to the steam control valve flow rate request signal 13 used for the turbine bypass valve 9. It is configured by adding to the lineage.

The operation of the apparatus shown in FIG. 1 constructed in this manner will be explained with reference to FIG. 2, assuming that frequency fluctuations similar to those shown in FIG. 6 have occurred.

Time 1 when the steam control valves 4a to 4d are not operated in the opening direction
For movement between 0 and 14, steam control valve flow rate request signal 1
3 and the actual valve passing steam flow rate 32 are controlled by limiters 17a to 17a provided in joint position control circuits 40a to 40d.
17d does not act in the valve closing direction, so the values are almost the same (actually, since there is a delay in the control operation in the position control circuits 40a to 40d, the steam control valve flow rate request signal 13 has a slightly low value, and this signal has a low value. In order to calculate the turbine bypass valve opening request signal 21 under these conditions, the turbine bypass valve opening request signal 21 and the main steam pressure 11b of the turbine bypass valve 9 are set as shown in FIG. Similarly, there is no change.

Assume that at time T4, the frequency that has once increased starts to decrease. At this time, the steam control valve flow rate request signal 13 changes in proportion to the rate of decrease in frequency, whereas the actual valve passing steam flow rate 32 is the flow rate determined from the actual steam control valve opening degree, so the actual steam control Changes according to the valve opening degree. Therefore, the low value of both is clearly the actual valve passing steam flow rate 32, and this signal is inputted via the low value priority circuit 33 to an arithmetic circuit for determining the turbine bypass valve opening request signal 21.

Therefore, the turbine bypass valve opening request signal 21 and the turbine bypass valve 9 are not affected by the steam control valve flow rate request signal 13, and perform a valve throttling operation in accordance with the amount of steam flowing into the steam turbine 5, thereby reducing the main steam pressure. Measures to prevent fluctuations in 11b.

Note that the steam control valve flow m request-valve lift correction circuit 14a~
14d and the valve lift/steam flow rate correction circuit 30 may have the same configuration, and only the human input signal and the output signal may be replaced.

FIG. 3 shows a second embodiment of the invention. In this embodiment, an adder 34 outputs a signal representing the difference between the steam control valve flow rate request signal 13 and the actual valve passing steam flow rate 32, and an adder 34 is provided which outputs a signal indicating the difference between the steam control valve flow rate request signal 13 and the actual valve passing steam flow rate 32, and when the output signal of this adder 34 exceeds a predetermined value. an on/off signal generator 35 that outputs an operating signal when A closing speed limiter 37 inserted into the position control circuit 41 is provided. Closing speed limiter 37
are designed to maintain the same response speed characteristics with the limiters 17a to 17d provided in the steam control valve position control circuits 40a to 40d, and are designed to maintain the same response speed characteristics between them and the steam flow rate to the steam turbine 5 side during operation. and the throttling ratio by the turbine bypass valve 9 on the turbine bypass valve 9 side are equal to each other.

FIG. 4 shows the behavior of each part of the device shown in FIG. 3 when the frequency fluctuates.

Between times 10 and 14, as already mentioned, the amount of steam passing through the steam control valve 4 is reduced and the turbine bypass valve 9
There is no main steam pressure fluctuation because the amount of bypass caused by After time T4, when the frequency fluctuation starts to recover, the levels of the steam control valve flow rate request signal 13 and the actual valve passing steam flow rate signal 32 shown in FIG. /Off signal generator 35 is turned on and actuates switching contact 36. Therefore, the closing speed limiter 37 is interposed in the turbine bypass valve position control circuit, and the turbine bypass valve opening request signal 21
varies with the steam control valve flow rate request signal 13, whereas the turbine bypass valve 9 itself is closed at a constant rate. Therefore, fluctuations in the main steam pressure 11b are suppressed as in the case of FIG. 3, making it possible to continue stable turbine operation.

According to the embodiments described above, even when the system frequency suddenly fluctuates, cooperative control of the steam control valve 4 and the turbine bypass valve 9 is achieved. Coordination with the amount of bypass steam is maintained, and fluctuations in main steam pressure can be prevented.

Although the above explanation has been made with reference to a nuclear power generation system, the present invention can be similarly applied to a thermal power generation system as long as it has a turbine bypass system, thereby improving the operation of the reboiler side. Operability can be improved.

〔Effect of the invention〕

According to the present invention, by implementing more complete cooperative control of the steam control valve and the turbine bypass valve, the amount of steam flowing into the steam turbine can be appropriately controlled even during sudden fluctuations in system frequency, and the main steam pressure can be increased. , thereby making it possible to further stabilize the operating characteristics of the plant.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a time chart showing the behavior of each control element during frequency fluctuation of the device shown in Fig. 1, and Fig. 3 is another embodiment of the present invention. FIG. 4 is a time chart showing the behavior of each control element during frequency fluctuations of the device in FIG. 3, and FIG.
The figure is a system diagram showing a typical configuration example of a known nuclear power plant, and FIG. 6 is a block diagram of a conventional steam turbine control device.
FIG. 7 is a time chart showing the behavior of each control element when the frequency of the device shown in FIG. 6 changes. 1... Nuclear reactor, 2... Main steam pipe, 3... Main steam stop valve, 4.4a to 4d... Steam control valve, 5... Steam turbine, 6... Condenser , 7... Generator, 8...
Turbine bypass system, 9...turbine bypass valve,
10... Speed control circuit, 10h... Speed control system output signal, 11... Pressure control circuit, 11h... Pressure control system output signal, 12... Low value priority circuit, 13... Steam Control valve flow rate request signal, 14a-14d...Steam control valve flow rate request-valve lift correction circuit, 15a-15d...Valve opening request signal, 21...Turbine bypass valve opening request signal, 30a-30d ... Valve lift - steam flow rate correction circuit, 32 ... Actual valve passing steam flow rate, 33 ... Low value priority circuit, 35 ... On/off signal generator, 36 ... Switching contact, 37.・・Closing speed limiter, 40a to 40d,
41... Part tif control circuit. Applicant's agent Mr. Sato Figure 2 Figure 4 Figure 7

Claims (1)

[Scope of Claims] 1. A first flow rate request signal generating means for outputting the lower value of the output signal of the speed control circuit and the output signal of the pressure control circuit as a steam control valve flow rate request signal; It has a function generator that determines the valve lift of the steam regulating valve in response to a regulating valve flow rate request signal, and a steam regulating valve position control circuit that controls the opening degree of the steam regulating valve based on the output signal of the function generator. a steam control valve control system; and a first control system formed based on the output signal of the pressure control circuit.
a second flow rate request signal generation means for outputting a difference between the input signal of the input signal and a second signal formed based on the steam control valve flow rate request signal as a turbine bypass valve opening degree request signal;
a turbine bypass valve control system having a turbine bypass valve position control circuit that controls the opening degree of the turbine bypass valve based on the turbine bypass valve opening degree request signal; A steam turbine control device, characterized in that the system is provided with a closing speed limiting means for achieving a closing speed matching the opening speed of the steam regulating valve controlled by the steam regulating valve control system. 2. As the closing speed limiting means, a second function generator that calculates the actual valve passing steam flow rate from the actual valve lift signal of the steam adjustment valve position control circuit; and the steam adjustment valve flow rate request signal and the second function. 2. The steam turbine control device according to claim 1, further comprising a low-value priority circuit that passes a low-value signal among the output signals of the generator and uses it as the second signal. 3. As the closing speed limiting means, an on/off signal generator that operates when the deviation between the steam regulating valve flow rate request signal and the output signal of the second function generator becomes larger than a predetermined value; The steam turbine control device according to claim 1, further comprising a closing speed limiter circuit for limiting the closing speed of the turbine bypass valve when the on/off signal generator is activated.