JPH0481503A - Turbine control device - Google Patents

Abstract

PURPOSE:To avoid unnecessary nuclear reactor scram due to a system disturbance and to improve an availability factor of a nuclear power plant by providing a changing rate limiting device which gives a changing rate characteristic corresponding to an actual operating speed of a steam adjusting valve to a speed control signal or a speed-load control signal. CONSTITUTION:A speed-load control signal G is output after an error signal between a turbine speed C detected by means of a speed sensor and a speed set value D has been multiplied by a gain constant K2 by means of an amplifier 24, and further, a load set value J has been added to it by means of an adder 26. When the speed-load control signal G is input to a changing rate limiting device 29, the speed-load control signal G is converted to the speed-load control signal H in this changing rate limiting device 29 so as to have a changing rate corresponding to an actual opening and closing speed of a steam governor valve. Because the opening speed of the governor valve is equal to the closing speed of a by-pass valve, and further, their increments are equal to each other, variation of main steam pressure A is prevented. Thus, it is possible to continue operation of the nuclear reactor while avoiding unnecessary nuclear reactor scram due to an electric power system disturbance.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a turbine control device, and in particular, when a turbine speed fluctuation occurs due to an electric power system disturbance, etc. The present invention relates to a turbine control device that allows nuclear reactor operation to continue without causing problems.

(Prior art) Fig. 3 is a diagram showing the main pipe system of a power generation plant, in which steam generated in a steam generator 1 passes through a main steam pipe 2, and its amount is controlled by a steam control valve 3. and flows into the turbine 4. This turbine 4 performs work and drives a generator 5 coaxially connected to the turbine 4 to generate electricity, and the electricity generated by the generator 5 is supplied to the grid 7 via a breaker 6. Ru. The steam that has done work in the steam turbine 4 is condensed in a condenser 8. Furthermore, the steam generated in the steam generator 1 that does not flow into the turbine 4 through the steam control valve 3 flows directly into the condenser 8 through the bypass valve 9.

On the other hand, the main steam pressure and turbine speed are detected by a pressure sensor 10 and a speed sensor 11, respectively, and these detected values are used as parameters for controlling the openings of the steam control valve 3 and bypass valve 9. Become.

FIG. 4 is a diagram showing an example of a control device for the steam control valve 3 and the bypass valve 9, in which the main steam pressure A detected by the pressure sensor 10 and the pressure setting value B set by the pressure setting device 20 are shown.
are added to the adder 21, and the adder 21 calculates the deviation between the two. Then, this deviation is multiplied by a gain of 1 in the amplifier 22 to produce the pressure control signal E. Here, 17
1 is generally called the pressure adjustment rate, for example, on the other hand,
A deviation between the turbine speed C detected by the speed sensor 11 and the speed setting value is also calculated in an adder 23, and the deviation is multiplied by a gain of 2 in an amplifier 24 to form a speed control signal F. Here, ]/2 is generally called the speed regulation rate, and for example, the speed control signal F is the load setter 25.
The adder 26 adds the load setting value J set in , and outputs the added signal as the speed load control signal G.

Both the pressure control signal E and speed load control signal G are input to the low value priority circuit 27, and the low value signal is outputted as a control valve flow rate request signal and is applied to the steam control valve 3 as a control signal. On the other hand, the pressure control signal E and the control valve flow rate request signal are also applied to the adder 28, and the deviation signal between the pressure control signal E and the control valve flow rate request signal becomes the bypass valve flow rate request signal. is added as a control signal.

In such a control device, during normal operation of the power plant, the load setting value J is usually set 10% larger than the regulating valve flow rate request signal during normal operation, so the pressure control signal E is higher than the speed. It becomes smaller than the load control signal G, the regulating valve flow rate load control signal becomes equal to the pressure control signal E, and the bypass valve flow rate request signal becomes zero. That is, all the steam generated by the steam generator 1 flows into the turbine 4 through the steam control valve 3, and the bypass valve 9 is controlled to be fully open.

Therefore, during normal operation, the speed control signal F consisting of the deviation between the speed setting value and the turbine speed C is within 10% (
The steam control valve 3 does not respond to the increase in turbine speed (corresponding to 0.25 Hz in the case of 50 Hz), and pressure control is performed preferentially.

On the other hand, when the speed control signal F increases by less than 10% (frequency increase of 0.25Hz or more in the case of 50Hz), the speed load control signal G changes to the pressure control signal E.
As a result, the steam control valve 3 is narrowed down. The surplus steam resulting from the throttling operation of the steam control valve is processed by the bypass valve 9, which is controlled to open by the bypass valve flow rate request signal K, which is a signal obtained by subtracting the control valve flow rate request signal from the pressure control signal E. . In this way, when the steam control valve 3 and the bypass valve 9 are operated in a coordinated manner, the reactor pressure hardly changes, and the plant operation can be stably continued.

(Problem to be Solved by the Invention) In this way, in normal operation, even if the turbine speed fluctuates, no problem occurs because the opening degrees of the steam control valve and the bypass valve follow the respective command values without delay. When a sudden disturbance occurs due to a system accident or the like, the following problems occur.

That is, as shown in the time chart of FIG. 5, if the turbine speed C suddenly increases from the reference speed at time t1 during pressure control operation, the speed load control signal G decreases,
From the time point t2 when the pressure becomes smaller than the pressure control signal E, the opening degree of the steam control valve 3 is decreased, and at the same time the bypass flow rate request signal K
increases, and the opening degree of the bypass valve 9 also increases.

In this case, since the closing operation amount of the steam control valve 3 and the opening operation amount of the bypass valve 9 are approximately equal in magnitude, no fluctuation occurs in the main steam pressure A. However, when the turbine speed C suddenly returns to the reference speed at time t4, the regulator valve flow rate request signal changes in the opening direction, and the bypass valve flow rate request signal changes in the closing direction.

In this case, are the change speeds and opening/closing amounts of the regulator valve flow rate request signal, the bypass valve flow rate request signal, and the bypass valve flow rate request signal the same, or the actual opening speed of the steam regulator valve 3 and the bypass valve The closing speed of the steam regulator 9 has different characteristics due to the mechanical constraints of the valve, and the opening speed of the steam control valve 3 lags behind the closing speed of the bypass valve 9, so the steam from the steam generator 1 is restricted and the main steam pressure A rises.

For this reason, the pressure control signal E changes in the opening direction, and the bypass valve 9 starts opening at time t and becomes fully open at time t8, at which point the pressure control exceeds the allowable control range, and at time t9, the main steam pressure A is limited. There is a risk that the value will be exceeded and the reactor protection interlock will be activated, leading to a reactor scram.

As a countermeasure to this problem, it may be possible to adjust the opening/closing characteristics of the steam control valve or bypass valve.Bypass valves are required to operate at extremely high speeds during load cut-off or when a turbine trip occurs, while control valves are It is difficult to improve the valve body due to structural and regulatory constraints.

In view of these points, the present invention provides a turbine control device that can continue reactor operation while avoiding unnecessary reactor scrams even when turbine speed fluctuations occur due to power system disturbances and the steam control valve opens and closes. The purpose is to obtain.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a steam control valve that controls the amount of steam generated in a steam generator flowing into a turbine, and a steam control valve that controls the amount of steam generated in the steam generator that does not flow into the turbine. and a bypass valve that controls the amount of steam released to a condenser etc., and the opening degree of the steam control valve and the bypass valve is controlled by a deviation signal between the main steam pressure and the set pressure and a deviation signal between the turbine speed and the set speed. In a turbine control device that controls turbine inlet steam pressure and turbine speed, a speed control signal consisting of a deviation signal between the turbine speed and a set speed or a speed load control signal corresponding to the actual operating speed of the steam control valve is used. The present invention is characterized in that a rate-of-change limiter is provided to provide a rate-of-change characteristic of .

(Function) As mentioned above, since the rate of change limiter is provided with a rate of change characteristic corresponding to the actual operating speed of the steam regulator valve, the steam regulator valve and the bypass valve are The opening/closing operation speed and operation amount match, and unnecessary fluctuations in turbine inlet steam pressure due to turbine speed fluctuations are prevented.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2.

The main steam pressure A detected by the pressure sensor is transferred to the pressure setting device 20.
The difference signal is compared with the pressure setting value B set in the adder 21, and the difference signal is multiplied by a gain of 1 in the amplifier 22 to become the pressure control signal E, which is sent to the low value priority circuit 27 and the adder 28.
is input.

On the other hand, the difference signal between the turbine speed C detected by the speed sensor and the speed setting value is multiplied by a gain of 2 in the amplifier 24 to become the speed control signal F, and the adder 26 uses the speed control signal F to set the load. The value J is added and the speed load control signal G is output.

Here, in the present invention, the speed load control signal G is input to the rate of change limiter 29. This change rate limiter 29 limits the change rate of the speed load control signal to match the actual opening/closing speed of the steam control valve, and the speed load control signal G is actually controlled in this change rate limiter 29. The speed load control signal H has a rate of change that matches the opening/closing speed of the steam control valve.

Then, this speed load control signal H is transmitted to the low value priority circuit 2.
7 is input.

On the other hand, the low value signal selected by the low value priority circuit 27 is
Similar to the conventional device, the signal is applied to the steam control valve as a control valve flow rate request signal, and is also input to the adder 28 and compared with the pressure control signal E, and the deviation signal is added to the bypass valve as a bypass valve flow rate request signal. .

FIG. 2 is a time chart showing the operation of the device shown in FIG. 1. During normal pressure control operation, when the turbine speed C starts to increase due to system disturbance at time t1, the speed load control signal H closes. At time t2, the speed load control signal H becomes the pressure control signal E, the regulator valve flow rate request signal changes in the valve closing direction, and the steam regulator valve is controlled in the closing direction. At this time, the bypass valve flow rate request signal changes in the valve opening direction by a deviation obtained by subtracting the regulating valve flow rate request signal from the pressure control signal E, and the bypass valve is controlled in the opening direction.

Therefore, when the turbine speed C starts to return to the reference value at time t4, the speed load control signal G increases at the same rate of change as the change in the turbine speed C, but the speed load control signal H increases due to the rate of change limiter 29. The load setting value J is returned to the target at a limited rate of change, that is, at a rate of increase corresponding to the opening speed of the control valve.

As a result, the control valve flow rate request signal rises due to the rate of change characteristic of the opening speed of the steam control valve itself, and at the same time, the bypass valve flow rate request signal is generated based on the pressure control signal E and the control valve flow rate request signal. Since it consists of a deviation, it decreases due to the rate of change characteristic of the speed in the opening direction of the steam control valve itself. Even if the turbine speed C returns to the reference value at time t6, the speed load control signal H is controlled by the characteristics of the rate of change limiter, so the actual opening degrees of the steam control valve and bypass valve also change. It is slowly controlled by the flow rate demand signal and the bypass valve flow rate demand signal K.

In this way, since the adjustment valve opening speed and the bypass valve closing speed are the same and the amount of change thereof is equal, fluctuations in the main steam pressure A are prevented.

In the above embodiment, the speed load control signal G is input to the rate of change limiter 29, but
On the speed side? Even if the a signal F is inputted to the rate of change limiter, it is exactly the same.

〔Effect of the invention〕

As explained above, in the present invention, a rate-of-change limiter is provided that gives the speed control signal or speed load control signal a rate-of-change characteristic corresponding to the actual operating speed of the steam control valve. When this occurs and the regulator and bypass valve open and close, the rate of change of the speed in the opening direction of the steam regulator and the speed in the closing direction of the bypass valve will be equal, especially even if the turbine speed suddenly changes to the return side after increasing. , the total flow rate of steam flowing through the steam control valve and the bypass valve does not change, and there is no fluctuation in the steam pressure at the turbine inlet. Therefore, in the nuclear coupler, unnecessary reactor scrams due to system disturbances can be avoided, and the operating rate of the nuclear coupler can be improved.

29... Rate of change limiter.

Claims (1)

[Claims] A steam control valve that controls the amount of steam generated in the steam generator flowing into the turbine, and a bypass valve that controls the amount of steam generated in the steam generator that does not flow into the turbine and is released to a condenser or the like. The opening degree of the steam control valve and the bypass valve is controlled by the deviation signal between the main steam pressure and the set pressure and the deviation signal between the turbine speed and the set speed, and the turbine inlet steam pressure and the turbine speed are controlled. In such a turbine control device, a rate-of-change limiter is provided to give a speed control signal or a speed load control signal consisting of a deviation signal between the turbine speed and a set speed a rate-of-change characteristic corresponding to the actual operating speed of the steam control valve. It is characterized by
Turbine control device.