JP2720032B2 - Turbine control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbine control device for controlling a steam pressurizing valve and an intermediate steam control valve of a boiling water nuclear power plant, and particularly to closing of the control valve when a system frequency rises. The present invention relates to a turbine control device suitable for controlling a quantity and preventing generation of unnecessary reactor scram. [Background of the Invention] A turbine control system performs a pressure regulation function of performing a reactor pressure control according to a detected pressure signal and a turbine output control according to a detected turbine speed signal and a load set value. It has both speed / load adjustment functions, and the signals of both control the coordinated control of the steam control valve, turbine bypass valve, and intermediate steam control valve. FIG. 2 is a block diagram for explaining the operation of the turbine control system in the prior art. In the figure, a pressure signal 1 measured by a pressure detector installed in a reactor or a main steam pipe is shown.
And a deviation signal from the preset pressure set value 2 is input to the pressure adjuster 4 through the filter circuit 3. The pressure regulator 4 creates a total main steam flow signal 5 based on the deviation signal. On the other hand, the deviation signal 8 between the turbine speed signal 6 measured by the turbine speed detector and the turbine speed set value 7 is input to the adjustable valve speed adjuster 9 and input to the adjustable valve opening arbiter 9,
The control valve control signal 10 is created. Further, a load / set value 11 which is an output signal of the load setting device is added to the control valve 10 to generate a speed / load control signal 12. In addition, the turbine speed deviation signal 8 is input to the intermediate control valve opening arbiter 14 to generate an intermediate steam control valve opening control signal 13. The load set value 11 is input to the CV adjustment rate / IV adjustment rate adjuster 16 and the created intermediate adjustment valve closing start point bias 17 and open bias 15 are added to the control signal 13 to create the intermediate adjustment valve flow signal 18. . CV represents a control valve steam control valve, and IV represents an intermediate valve intermediate steam control valve. The total steam flow signal 5 and the speed / load control signal 12 thus calculated are input to the low value priority circuit 19, and the lower one of the two signals is used as the control valve flow request signal 20 to control the control valve opening degree. Become. On the other hand, the degree of opening of the bypass valve is controlled by a bypass valve flow request signal 22 obtained by subtracting the control valve flow request signal 20 and the bypass valve chattering preventing bias signal 21 during normal operation from the total main steam flow signal 5. At a boiling water nuclear power plant, reactor power is adjusted by the amount of voids (steam bubbles) in the reactor core, so neutrons are sensitive to changes in pressure. Therefore, during normal operation, the control valve is preferentially controlled by the total main steam flow signal 5 based on the pressure signal, and the load set value is controlled so that the control valve does not operate with a relatively small change in turbine speed.
11 is set to about 10% or more of the total main steam flow signal 5. Therefore, if the opening / closing valve opening request signal 10 is within -10% (generally, the speed regulation rate is 100% control signal / 5% speed change, and the 10% opening request signal is 50%) The control valve does not respond to the turbine speed increase of (equivalent), and pressure control is performed preferentially. On the other hand, for a turbine speed increase (frequency increase of 0.25 Hz or more) at which the speed / load control signal 12 decreases by 10% or more, the speed / load control signal 12 becomes less than or equal to the total main steam flow signal 5 and a low value. The speed / load control signal 12 is selected by the priority circuit, and the throttle operation of the control valve is performed. At this time, the excess steam generated by the throttle operation of the control valve is used as a bypass valve flow request signal obtained by subtracting the control valve flow request signal 20 and the bias value 21 from the total main steam flow signal 5.
By 22 the bypass valve is opened and processed. In this way, the throttle valve is throttled to increase the turbine speed (0.25 Hz or more) to reduce the load, thereby preventing the turbine speed from increasing.
At that time, the control valve and the bypass valve cooperate with each other, so that the reactor pressure can hardly change and the plant operation can be stably continued. Next, the response of the nuclear power plant when settling after a 0.5 Hz turbine speed increase due to a system accident will be described with reference to FIG. If an accident such as a lightning strike occurs in the transmission system and the load is partially lost due to the effect, the system frequency will increase (assuming a 0.5 Hz increase). Thereafter, when the fault is removed by the protection operation, the system frequency is settled to a steady value. At this time, the turbine speed also follows the system frequency. As a result, the opening / closing valve opening control signal 10 becomes a negative value, and the speed / load control signal 12 is also narrowed down from the normal signal. When the turbine speed increases by about 0.25 Hz, the speed / load control signal 12 becomes equal to or less than the total main steam flow signal 5, and the output of the low value priority circuit 19 switches to the speed / load control signal 12 side. Therefore, the regulating valve is
It is throttled as the speed / load control signal 12 decreases, reducing turbine output. The control valve is reduced by 10% for 0.5Hz system frequency rise. However, all excess steam is led directly to the condenser through the bypass valve, so that the reactor pressure fluctuates little and the neutron flux fluctuates only slightly. For such a relatively small increase in the system frequency, excess steam generated when the control valve is throttled can be processed by the bypass valve. On the other hand, in a nuclear power plant with a bypass valve capacity of 25%, the system frequency rise (0.82
(5Hz or more), the surplus steam cannot be completely processed, and the neutron flux rises due to a mismatch in the main steam flow rate, leading to scram. The response of the nuclear power plant when the system frequency increases by 1.5 Hz will be described with reference to FIG. As shown in the figure, the speed control signal is
0%, which results in a 50% speed / load control signal (assuming a load setting of 110%). As a result, the valve opening is reduced from 100% to 50%. At the same time, a request signal to open the bypass valve by 50% is issued, but even if it is fully opened, only 25% of excess steam can be processed, so the reactor pressure rises, the neutron flux rises sharply, and exceeds 120% At this point, a neutron flux scram is reached. As shown above, in the boiling water nuclear power plant with 25% turbine bypass capacity, it can be seen that a frequency fluctuation of 0.825 Hz or more leads to a scram (high neutron flux).
Although a system frequency increase of 0.825 Hz or more is a rare event, of course, if a 25% turbine bypass plant reaches the entire plant scram, power shortages will occur, conversely, the system frequency will decrease, and accidents may increase. There is. Since restarting of a nuclear power plant requires a certain amount of time, there is a problem that the restoration of the system is delayed and the operation rate is reduced. [Object of the Invention] An object of the present invention is to provide a turbine control device capable of preventing generation of unnecessary scrum due to an increase in system frequency (turbine speed) that occurs when an accident occurs in a power transmission system. [Summary of the Invention] Since the conventional device simply adjusts the closing amount of the control valve when the system frequency rises in proportion to the system frequency increase width, the scram is particularly required in a 25% turbine bypass plant by increasing the frequency by 0.825 Hz or more. Focusing on the points leading to the above, first, the control valve adjustment rate is made frequency dependent, limiting the closing amount of the control valve, and maintaining the coordinated control of the control valve and the intermediate control valve, the CV adjustment rate / IV The regulation rate is also frequency-dependent, and prevents the occurrence of scram when the system frequency rises, which does not require the reactor to be scrammed at about 1.5 Hz. That is, in order to achieve the above-mentioned object, the present invention provides a method for measuring the total pressure based on a deviation of a measured value of a pressure detector arranged in a reactor or a main steam pipe of a boiling water nuclear power plant and a predetermined pressure set value. The steam flow signal is compared with the speed / load control signal obtained by adding the set value of the load setting device to the control valve opening control signal based on the measured value of the turbine speed detector and the deviation signal of the predetermined speed set value, and is low. Control the valve opening as a control valve flow request signal, and control the bypass valve opening as a bypass valve flow request signal by subtracting the control valve flow request signal from the total main steam flow signal. The intermediate steam control valve opening control signal based on the speed deviation signal is added to the intermediate steam control valve closing start point bias based on the set value of the intermediate steam control valve bias load setting device, and the intermediate steam control valve flow rate signal is added. A turbine control device for controlling an intermediate steam control valve opening by controlling a control valve opening control signal according to a frequency from the turbine speed deviation signal; Turbine control provided with a steam regulator / intermediate steam regulator regulating function generator for setting an intermediate steam regulator closing start bias to a frequency equal to or higher than a frequency at which the regulator is fully closed based on a setting value of a setter. Suggest a device. Embodiment of the Invention Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows the control valve / bypass valve and the intermediate steam control valve flow request signal calculation circuit in the turbine control system. In the figure, a turbine speed deviation signal 8 is converted into an adjustable valve opening control signal 10 by a frequency dependent type adjustable valve opening adjustment rate function generator 23, added to a load set value 11, and a speed / load control signal 12 Becomes This speed / load control signal 12
And the total main steam request signal 5 are input to the low value priority circuit 19, and the lower one of the two signals controls the control valve as the control valve flow request signal 20. The turbine speed deviation signal 8 is converted into an intermediate control valve opening control signal 13 by an intermediate steam control valve opening adjuster 14, and the load set value 11 is further converted to a frequency-dependent CV setting rate / IV setting rate function. The intermediate steam control valve closing start control signal 17 converted by the generator 24 is added to the control signal 17 to control the intermediate steam control valve as an intermediate steam control valve flow request signal 18. The bypass valve is a bypass valve flow request signal 22 obtained by subtracting the control valve flow request signal 20 and the bypass valve chattering prevention bias signal 21 during normal operation from the total main steam flow signal 5.
The opening is controlled by. Here, a 25% capacity turbine bypass plant, 1.
The effect will be described using a frequency dependent CV regulation rate and a frequency dependent CV regulation rate / IV regulation rate as an example to prevent scram against a 5 Hz frequency rise. FIG. 5 shows the relationship between the frequency increase width (speed control signal) at the frequency dependent type regulating valve regulation rate and the regulating valve closing request. Even if the system frequency rises by 1.5 Hz, the adjustment valve closing request is 30
%, And a bias of + 10% is added to this.
The actual closing requirement is 20%. Therefore, even if the frequency rises by 1.5 Hz, all of the excess steam can be processed by the bypass valve without closing the control valve to the bypass capacity or more. FIG. 6 shows the relationship between the system frequency and the control valve flow request signal when the load setting is 110% (actual load 100%). Until 51.5Hz, the flow rate control valve requirement will not fall below 80%. Next, the load setting when the adjustment valve opening / closing ratio is frequency dependent and the CV / IV adjustment ratio is (5/2) as before.
FIG. 7 shows the flow demand signals of the regulator and intermediate steam regulator at 40% (30% actual load) as a function of frequency. As shown in FIG. 7, when the CV adjustment rate / IV adjustment rate is the same as before, the intermediate steam control valve starts to close before the control valve fully closes, so that the intermediate steam pressure may increase. On the other hand, if the CV adjustment rate / IV adjustment rate is frequency-dependent as shown in FIG. 8, the intermediate adjustment valve starts closing after the adjustment valve closes as shown in FIG. Control method. This is unchanged at any load setting. As shown above, the control valve opening adjustment rate and CV adjustment rate / IV
If the adjustment rate is frequency-dependent, the reactor will not scram when the frequency rises to 1.5 Hz, and the coordination between the control valve and the intermediate steam control valve can be maintained as before. [Effects of the Invention] According to the present invention, when the control valve is throttled when the system frequency rises, the bypass valve capacity is reduced for a frequency rise that allows continuous operation in order to throttle the control valve according to the system frequency. As described above, since it is not necessary to throttle the control valve, an increase in the reactor pressure is prevented, and the occurrence of a high neutron flux scram is prevented. At the same time, the CV adjustment rate / IV adjustment rate is also frequency-dependent, so that the coordination between the control valve and the intermediate steam control valve is ensured, and the plant durability against the system frequency rise can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram for explaining an embodiment of a turbine control device according to the present invention, FIG. 2 is a block diagram of a conventional turbine control device, and FIG. Fig. 4 shows the transient response when rising, Fig. 4 shows the frequency of 1.5Hz in the conventional device
FIG. 5 is a diagram showing a transient response at the time of rising, FIG. 5 is a diagram showing an example of a frequency-dependent regulating valve opening / closing rate, FIG. 6 is a diagram showing a relationship between a frequency and a regulating valve flow signal according to the present invention, The figure shows the relationship between CV and IV when the CV setting rate / IV setting rate is not changed, FIG. 8 shows the frequency-dependent CV setting rate / IV setting rate, and FIG. 9 shows the frequency-dependent CV setting rate. CV by fixed rate / IV adjustment rate
FIG. 4 is a diagram showing a relationship between and IV. 1 ... pressure signal, 2 ... pressure set value, 3 ... filter circuit, 4 ... pressure regulator, 5 ... total main steam flow rate signal, 6 ...
... turbine speed signal, 7 ... turbine speed set value, 8 ...
... Deviation signal, 9 ... Adjustable valve opening adjuster, 10 ... Adjustable valve opening control signal, 11 ... Load set value, 12 ... Speed / load control signal, 13 ... Intermediate opening and closing valve opening control Signal, 14 …… Intermediate steam control valve opening adjuster, 15 …… Intermediate steam control valve bias,
16 CV adjustment rate / IV adjustment rate adjuster, 17 Intermediate control valve closing start point bias, 18 Intermediate control valve flow signal, 19
Low value priority circuit, 20: Adjustable valve flow request signal, 21: Anti-chattering bias signal, 22: Bypass valve flow request signal, 23: Frequency-dependent function generator for opening / closing valve opening adjustment rate, 24 ... … Function generator for frequency dependent CV setting rate / IV setting rate.

Claims (1)

(57) [Claims] The measured value of the pressure detector installed in the reactor or main steam pipe of the boiling water nuclear power plant and the total main steam flow signal based on the deviation of the predetermined pressure set value and the measured value of the turbine speed detector and the A control value based on a deviation signal of a predetermined speed set value is compared with a speed / load control signal obtained by adding a set value of a load setting device to a control valve opening / closing control signal. Control the bypass valve opening as a bypass valve flow request signal using a value obtained by subtracting the control valve flow request signal from the total main steam flow signal, and control the intermediate steam control valve opening control signal based on the turbine speed deviation signal. A value obtained by adding the intermediate steam control valve opening bias and the intermediate steam control valve closing start point bias based on the set value of the load setter to the intermediate steam control valve flow signal is used as the intermediate steam control valve opening signal. In the bin control device, a function generator for an adjustable valve opening adjustment rate that calculates an adjustable valve opening control signal depending on a frequency from the turbine speed deviation signal, and the adjustable valve based on a set value of the load setting device. A turbine control device comprising: a steam control valve / intermediate steam control valve setting rate function generator for setting an intermediate steam control valve closing start point bias to a frequency equal to or higher than a frequency at which the valve is fully closed.