JPS61110083A - Load follow-up controller for boiling water type nuclear power plant - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a load following control device for a boiling water nuclear power plant, and is particularly suitable for use when the range of load fluctuation is small and the fluctuation cycle is short. This invention relates to a load following IIJ control device for a boiling water nuclear power plant, which follows the load by so-called governor-free operation.

[Technical background of the invention and its problems]

In recent years, as the proportion of nuclear power plants in the electric power system has increased, there has been an increasing need to switch the operation of nuclear power plants from conventional rated base load operation to load following continuous operation.

In general, power demand has large seasonal, daytime, and nighttime fluctuations, as well as small load fluctuations at all times.In order to keep the frequency of the power system constant in response to these load fluctuations, the power supply of this power system is On the other hand, power plants control their electrical output using the so-called grid automatic frequency I+11.
1211 (AFC) is being performed.

Therefore, if nuclear power plants are to increase their supply share in the power system in the future, automatic frequency control operation of the power system at night will be necessary, in addition to daily output adjustment operation that corresponds to each daytime and nighttime power demand. becomes. This is because thermal power plants, which have traditionally been responsible for automatic frequency control of the electric power system, stop operating in response to the drop in power demand at night, and output adjustment that takes part in automatic frequency control of the electric power system is required. This is because the amount decreases.

FIG. 3 shows an example of the distribution of output control on the power plant side with respect to such load fluctuations in the power system.

In other words, the vertical axis shows the magnitude of load fluctuations, and the horizontal axis shows the cycle of load fluctuations. Regarding fluctuations, appropriate daily output adjustments are made based on instructions from a central power dispatch control center (not shown) of the power system.

Regarding this, the present patent applicant has already filed a patent application for [Load following automation device for nuclear power plants] (Japanese Patent Laid-Open No. 55-20
404 Publication)). In addition, regarding load fluctuations from fluctuation period A (for example, about 20 seconds) to fluctuation period B, the required output adjustment amount is usually calculated by the self-control device in the central power dispatch control room of the power system. This is distributed in appropriate proportions to the power plants that share frequency control within the system, and is transmitted as an AFC intermediate feed signal. Each power plant that receives this signal adjusts its output based on this signal. Regarding this automatic frequency control (AFC) device for boiling water type nuclear power generation plants, for example, the applicant of the present patent has filed a patent application [Output IL Control Device for Boiling Water Type Nuclear Power Plants (Japanese Patent Application Laid-Open No. 59-54997 publish)
detailed in.

For high-frequency components with a fluctuation period of A or less, each power plant must open the turbine artificial governor valve (main steam control valve) by l.
This is handled by so-called governor-free operation. This governor-free operation starts from the turbine! The machine speed is compared with a set value, the deviation is fed back to the turbine, and the opening of the turbine artificial governor valve (main steam control valve) is controlled so that this deviation becomes zero.
Conventional nuclear power plants did not perform governor-free operation. However, due to the circumstances mentioned above,
Today, governor-free operation is required even in nuclear power plants. Further, when performing this governor-free operation, it is desirable that cooperation with automatic frequency control 6j (AFC) operation be sufficiently taken into consideration.

By the way, the feature of governor-free operation is that, as shown in Figure 3, it targets load fluctuations with relatively short fluctuation cycles, and at the same time, the range of fluctuations is relatively small, and the amount of output adjustment required is is small. Therefore, in boiling water nuclear power plants, output adjustment is not necessarily required when performing governor-free operation by utilizing the inertia of the reactor system, such as the mass of fluid in the reactor pressure vessel and main steam pipe, and the inertia of internal energy. I don't.

Figures 4 and 5 show what happens in a boiling water nuclear power plant when the main steam flow rate to the turbine increases or decreases for a short time without recirculation or control rod operation to adjust the output. 2 is a graph showing the response of reactor pressure (Kl/d) and thermal output (% rating), respectively. As shown in FIG. 4, when the main steam flow ff1 (%) to the turbine is increased by a small amount and for a short period of time, the reactor pressure decreases in a quadratic curve. However, the thermal power in the core remains largely unchanged initially.

This indicates that the reduction in reactor pressure has little effect on thermal output. Furthermore, on the contrary, as shown in Figure 5, even when the main steam flow m (%) to the turbine is reduced by a small amount 1 and for a short time, the reactor pressure increases in a quadratic curve. However, the thermal output hardly changes at the initial stage, indicating that a decrease in reactor pressure has little effect on the thermal output.

Therefore, from the above, the fluctuation period of load fluctuation is relatively short, for example, about 20 seconds or less, and
If the range of variation is small, governor-free operation can be performed using the inertia of the reactor system without causing large fluctuations in the thermal output of the reactor. That is,
Generally, in an 8-channel water type nuclear power plant, the turbine steam 2
! When m, that is, the load is increased, the reactor pressure decreases and steam bubbles (voids) in the reactor core increase, and the negative reactivity effect of these steam bubbles causes a reverse response in which the reactor output decreases. It was confirmed that such reverse responses do not need to be taken into account if the load fluctuations are limited to short-term load fluctuations.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and it is possible to quickly increase the output of the turbine generator in response to minute fluctuations in power demand.
It is an object of the present invention to provide a load follow-up control device for a boiling water nuclear power plant that reliably follows the load.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention aims to reduce the thermal output at the beginning of the fluctuation due to the inertia of the boiling water reactor system when the fluctuation period of the turbine load fluctuation is short and the fluctuation width is small. It was created by focusing on the fact that there is almost no variation, and it is structured as follows. In a boiling water nuclear power plant having a pressure 2i1160 system that controls the reactor pressure of the boiling water reactor to always maintain it at a predetermined pressure, and a turbine control system that appropriately controls the rotation speed of the turbine, the turbine ! A high frequency filter that extracts a high frequency component in a governor free operating region from a turbine speed deviation signal obtained by removing a load setting bias from a turbine load request signal in a 1IIa system and outputs a high frequency turbine speed deviation signal, and this high frequency turbine. a limiter that appropriately limits the amplitude of the speed deviation signal and adjusts it to a required output regulating valve to form a governor free operation request signal and applies it to the pressure adjustment signal of the pressure control system; and a pressure set value changer that changes the required pressure set value of the pressure control system to stop the reactor pressure control by this pressure control system, and the governor free operation is applied to the pressure adjustment signal. It is characterized in that the opening degree of the main steam control valve is controlled by a request signal to cause the turbine generator output to follow load fluctuations.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of an embodiment of a load following AIL control device for a boiling water nuclear power plant according to the present invention, and reference numeral 1 in the figure indicates a boiling water nuclear reactor. A reactor core 2 is housed in the reactor 1 in a state where it is submerged with reactor water, and the reactor water is heated by the reaction heat of the nuclear fuel loaded into the reactor core 2 to generate steam. The nuclear reactor 1 is connected to a turbine 4 via a main steam pipe 3, and the main steam generated in the reactor 1 is introduced into the turbine 4 via the main steam pipe 3 to do work, and the output shaft 5 of the turbine 4 A turbine generator (not shown) directly connected to the generator is driven to generate electricity, and the power is supplied to an electric power system (not shown).

A main steam control valve 6 is installed in the main steam pipe 3 near the main steam inlet of the turbine 4 to adjust the amount of steam flowing into the turbine 4.

A turbine bypass pipe 7 is connected midway in the main steam pipe 3 on the upstream side of the main steam control valve 6, and the other end of the turbine bypass pipe 7 is connected to a bypass valve 8 midway through which the turbine 4 is restored. It is connected to a water container 9. The turbine bypass valve 8 opens when the load on the turbine 4 is significantly reduced.
A decrease in the amount of main steam flowing into the turbine 4 is directly bypassed to the condenser 9 to suppress a sudden rise in pressure within the reactor 1.

The boiling water nuclear power plant configured in this manner further includes a pressure 111 control system A that controls the pressure in the reactor 1 to always maintain it at a predetermined pressure, and a turbine' that controls the rotational speed of the turbine as appropriate. 11jtill system B, and the pressure control system A has a pressure detector 1 that detects the turbine inlet pressure.
1 is provided on the turbine inlet side of the main steam pipe 3. The turbine inlet pressure detected by the pressure detector 11 is inputted as a turbine inlet pressure signal 11A to the pressure comparator 12, where it is compared with the pressure set value set by the pressure setting device 13 and the set value is determined. The deviation is calculated and the pressure deviation signal 1
The pressure f is input to the IJ all ifi device 4 as 2A. In this pressure DI III lη14, this pressure deviation signal 12A is converted into the opening degrees of the main steam control valve 6 and the turbine bypass valve 8, respectively, and the pressure adjustment signal 14 is
A and sends it to the low value priority circuit 1 via the adder 15.
6 and a servo adder 17, respectively. Although the control signal from the turbine ilI1g system B is also input to the low value priority circuit 16, the pressure adjustment signal 14A of the pressure control system A having a low value is normally given priority, and the main steam control valve servo 18 and the turbine bypass valve are The signals are input to the servo 19, respectively.

The main steam control valve servo 18 and the turbine bypass valve servo 19 adjust the opening degree of the main steam control valve 6 and the turbine bypass valve 8 to 11 Jt so that the pressure deviation from the pressure setting value becomes zero.
Do ll. Thereby, the pressure inside the nuclear reactor 1 is always kept constant.

On the other hand, the turbine control system B includes a turbine speed detector 20 on the output shaft 5 of the turbine 4 to detect the rotational speed (frequency) of the turbine 4 and the turbine power generation m<not shown. The rotational speed of the turbine 4 detected by the turbine speed detector 20 is inputted as a turbine speed signal 20B to the speed comparator 21, where it is compared with the speed setting value set by the speed setting device 22 to determine the deviation. is calculated. This speed deviation signal 21B is input to the speed adder 23, where it is input to the load setting bias generator 24 and the load setting device 2.
The load setting bias and load setting value output from 5 are
are added to form a turbine load request signal 23B, which is output to bias subtractor 26 and low value priority circuit 16, respectively. As mentioned above, the pressure adjustment signal 14A from the pressure control system A is also input to the low value priority circuit 16, but the turbine load request signal 2 of the turbine control system B is also input to the low value priority circuit 16.
3B is already biased, the low value pressure adjustment signal 14A normally takes priority, and the pressure adjustment signal 14A is output to each servo 18, 19 with priority, respectively. This is to give priority to the pressure mall system A over the turbine control system B, since generally there is always a positive feedback on the influence of pressure changes in the reactor system on the output.

On the other hand, the turbine load request signal 23B input to the bias subtracter 26 is once again removed from the added bias by the speed adder 23, and the turbine speed deviation signal 23B is
B and is input to the pressure set value regulator 27 and high frequency filter 28, respectively. This pressure set value regulator 2
7 appropriately adjusts the pressure setting value input to the pressure comparator 12 to stop the reactor pressure control operation by the pressure control system A, and in the meantime controls the rotational speed of the turbine 4 by the turbine v111II system B. But pressure! l
I Ia outfit! Since it is extremely difficult to adjust the constants with f14, it is not reliable and is hardly used in actual plants.

Furthermore, high frequency components in the governor free operating region are extracted from the turbine speed deviation signal 26B input to the high frequency filter 28, and PIA (low frequency components) longer than the load fluctuation cycle A shown in FIG. 3 are removed. . For load fluctuations in the high frequency region shorter than the fluctuation period A, the load is followed by governor-free operation, and in the low frequency region longer than the fluctuation period A, as shown in Figure 3, automatic frequency control and daily This is to share the responsibility for output adjustment. The high frequency turbine speed deviation signal 28c of the high frequency component extracted by the high frequency filter 28 is input to the limiter 29,
Here, the amplitude is limited to the required width, and the turbine load request is adjusted to be below the limit allowed by the inertia of the reactor system (for example, several percent rated output), and the governor free operation request signal 29C is formed and added. device 15 and pressure set value change device 30
are output respectively. Governor free operation request signal 29C added with pressure adjustment signal 14A by this adder 15
are input to the main steam control valve servo 18 and the turbine bypass valve servo 19 via the low value priority circuit 16 and the servo adder 17, respectively. These servos 18 and 19 respectively control the opening degrees of the main steam control valve 6 and the turbine bypass valve 8 in accordance with the load request of the governor free operation request signal 29c, and make the output of the turbine 4 follow negative fluctuations. . By the way, when the fluctuation cycle of this load fluctuation is about 20 seconds, when the opening degree control of both valves 6 and 8 is performed, the reactor pressure fluctuates.

As a result, the pressure detector 11 of the pressure control system A detects this pressure fluctuation, and the pressure t and the reactor pressure tsvitim function of the IJ control system A are adjusted so that the deviation from the pressure set value is zero, and the governor The load following effect of free running is lost over time. Therefore, in response to the governor free operation request signal 29c, the pressure set value changer 30 transmits a pressure set value change signal 30c to the pressure comparator to change the pressure set value of the pressure setting device 13 in a direction in which the governor free operation is continued. Output to 12.

That is, the pressure set value changer 30 generates the pressure set value change signal 3 by using a coefficient for converting the governor free operation request (load request of No. g 29G into a pressure set value change) and a required transfer function.
0c is formed as appropriate, and a -order lag, for example, can be used as the required transfer function.

In addition, when performing the above-mentioned governor free operation, the use of the pressure set value regulator 27 is stopped and the high frequency filter 28 is
, limiter 29, and pressure setting value changer 30.

In addition, the reactor output of reactor 1 was changed to M by the m1mm5ua system.
This is adjusted by appropriately controlling the G upper set drive motor to drive the recirculation pump.

Next, the operation of this embodiment will be described.

Here, for example, when the load on a turbine generator (not shown) increases, the turbine control system B such as the turbine speed detector 20 detects a decrease in the rotational speed (frequency) of the turbine 4,
The turbine load request signal 23B is output to the low value priority circuit 16 and the bias reducer 26, respectively. The bias subtracter 26 removes the load setting bias from the turbine load request signal 26B and outputs the turbine speed deviation signal 26B to the high frequency filter 28. A high frequency component that is a target of governor free operation is extracted by a high frequency filter 28,
Low frequency components that are subject to automatic frequency control (AFC) and the like are removed. This high frequency targon deviation signal 28c is input to the limiter 29, where the output is adjusted within a range where the inertia of the main steam pressure of the reactor can be utilized, that is, within the permissible limit for fluctuations in the main steam pressure. The amplitude of this high frequency turbine deviation signal 28c is limited to form a governor free operation request signal 29C. The governor free operation request signal 29c is output to the pressure set value changer 30 and the adder 15, respectively. This governor free operation request signal 29G
The main steam control valve servo 18 receives the input and opens the main steam control valve 6 in the direction of increasing the opening so that the turbine speed deviation becomes zero.

As a result, the main steam inflow mountain into the turbine 4 increases, the rotational speed of the turbine 4 is accelerated, and the power generation output is
It is possible to quickly and reliably follow load fluctuations by increasing the amount corresponding to the increase in load.

When the turbine load request signal 23B has a rectangular waveform with a period of about 10 seconds, for example, as shown in FIG.
responds well to

Moreover, the fluctuation range of the reactor pressure is 0.2 kg/CI at the peak value.
i, and the fluctuation width of the neutron flux is less than 2% at the peak value, so there is no problem.

However, when the fluctuation period of load fluctuation is, for example, about 20 seconds, the pressure control system A operates to perform the reactor pressure control function, and the load following effect of governor free operation is lost. Therefore, the pressure setting value changer 3゜0 to which the governor free operation request signal 29c is input changes the pressure setting value of the pressure setting device 13 to a pressure lower than the pressure before inputting the governor free operation request signal 29c. Set value change signal 30G
is output to the pressure control system. For this reason, even if the reactor pressure decreases due to governor-free operation, as long as this decrease is within the change range, no pressure deviation will occur, and the pressure ail
The pressure compensation function of the LTLL system prevents loss of the load following effect of governor free operation. Moreover, during this governor-free operation, as described above, the thermal output of the nuclear reactor 1 is stable with almost no fluctuation at the beginning of load fluctuation.

〔Effect of the invention〕

As explained above, the present invention performs governor-free operation within the range in which the inertia of the reactor system can be utilized, so that the nuclear power plant can quickly and efficiently respond to load requests in the governor-free operation range with short fluctuation cycles. Moreover, it is possible to reliably follow the load, and is effective for the frequency tIIIall of the power system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of a boiling water nuclear power plant according to the present invention, and FIG. 2 is a response of the reactor system to a turbine load request signal in the embodiment shown in FIG. 1. Graphs showing examples. Figure 3 is a graph showing a general load fluctuation curve of an electric power system together with an example of distribution of power plant output 1lIlll. Figures 4 and 5 are reactors in a typical boiling water nuclear power plant. It is a graph for explaining each inertia of the system. 26... Bias subtractor, 26B... Turbine speed deviation signal, 28... High frequency filter, 28c... High frequency turbine speed deviation signal, 29... Limiter, 29C
...Governor free operation request signal, 30...Pressure set value change device, 30G...Pressure set value change signal. Figure 2 Figure 3

Claims (1)

[Claims] In a boiling water nuclear power plant having a pressure control system that controls the reactor pressure of the boiling water reactor to always maintain it at a predetermined pressure, and a turbine control system that appropriately controls the rotation speed of the turbine, the turbine A high frequency filter that extracts a high frequency component in a governor free operating region from a turbine speed deviation signal obtained by removing a load setting bias from a turbine load request signal in a control system and outputs a high frequency turbine speed deviation signal, and this high frequency turbine. a limiter that appropriately limits the amplitude of the speed deviation signal and adjusts it to a required output adjustment amount to form a governor free operation request signal and applies it to the pressure adjustment signal of the pressure control system; and a pressure set value changer that changes the required pressure set value of the pressure control system in response to the governor free operation request applied to the pressure adjustment signal and stops the reactor pressure control by the pressure control system. A load follow-up control device for a boiling water nuclear power plant, characterized in that the opening degree of a main steam control valve is controlled by a signal to make a turbine generator output follow load fluctuations.