JPS63154807A - Turbine controller having nonlinear characteristic - Google Patents

Abstract

PURPOSE:To expand the system frequency ceiling of a plant as well as to avoid causing a reactor scram, by giving a nonlinear characteristic to a governing valve permanent speed variation, and holding governing valve opening in a certain frequency range. CONSTITUTION:In case of a turbine controller of a plant having a partial capacity turbine bypass valve, a deviation C between a turbine speed setting signal B and a turbine speed signal A is found by an adder 1, feeding it to another adder 12. And, this speed deviation C is inputted into the adder 12 via a function generator 11, and the nonlinearized speed deviation signal R is outputted. A governing valve is controlled by a lowered value signal in a signal E adding a load setting signal F to this signal R and a steam flow signal M. With this constitution, even to a rise in system frequency, governing valve opening is controlled so as not to close it in a certain frequency range, so that a system frequency ceiling of the plant is expandable.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a control device for a steam turbine, and particularly to a control device for a steam turbine.

The present invention relates to a control device suitable for a power generation steam turbine equipped with a partial capacity turbine bypass valve.

[Conventional technology]

Generally, in a generator-driven turbine (for example, a steam turbine combined with a boiling water reactor), under normal conditions,
Although it is operated at a speed that matches the frequency of the power grid,
In the case of a large-scale load shedding in a power system, there is a risk that the grid frequency will rise due to turbine overspeed. The steam regulating valve is closed according to the regulation rate to prevent the turbine from overspeeding, and at the same time the turbine bypass valve is opened and the excess steam is sent to the condenser. When the turbine bypass valve capacity is exceeded, the reactor pressure increases, eventually leading to a high neutron flux scram. In recent years, the proportion of atomic couplers in power systems has been increasing, and it is necessary to be able to continue plant operation without easily scrubbing 11 in response to constant system frequency fluctuations.

Regarding the control of this type of turbine,
The technology of the No. 02 turbine controller is known.

FIG. 2 is a steam system diagram of a steam turbine in a boiling water atomic coupler.

Steam emitted from the nuclear power plant 101 passes through a main steam stop valve 103 and a steam control valve 104, and flows into a high pressure turbine 105.

The steam leaving this high pressure turbine 105 is sent to a moisture separator 106
a, 106b, intermediate steam stop valves 107a to 107
f, intercept valves 108a to 108f, and flow into the low pressure turbines 109a to 109C, and the respective exhaust gases are led to the condenser 111. The water condensed in the condenser 111 is returned to the reactor 10 by the reactor feed water pump 112.
Returned to 1. When the amount of steam generated from the reactor is large compared to the steam flow rate required by the turbine, excess steam is directly flowed to the condenser 111 through the turbine bypass valve 102'. It is connected to the power system via the main circuit breaker 113.

Fig. 3 is a control system diagram showing the configuration of a known technology related to a control device for a steam turbine in a boiling water plant. Calculate the deviation from the speed setting signal that sets the speed.

2 is an amplifier, and 3 is an adder, to which the output of the amplifier 2 and a load setting signal are applied, and a steam control valve flow rate request signal is extracted.

Reference numeral 6 denotes an adder, to which the output of the amplifier 4 and the load setting signal of the intercept valve corresponding to the load setting extracted by the amplifier 5 are applied, and the intercept valve flow rate signal is extracted. The above-mentioned components (1 to 6) allow the speed/
A load control circuit is configured. 8 is an adder to which a pressure signal obtained by detecting the pressure of steam generated from the R sub-furnace and a pressure setting signal for setting the steam pressure are given. 9 is an amplifier, and these components (8, 9) constitute a pressure control circuit. 7 is a low value priority circuit that compares the steam regulator flow rate request signal from the speed/load control circuit and the output signal of the pressure control circuit, passes only the low value signal with priority, and controls the steam regulator flow rate. Extract the signal. Reference numeral 10 denotes an adder, which is supplied with the output signal of the pressure control circuit and the steam control valve flow rate signal from the low value priority circuit 7, and extracts the turbine bypass valve flow rate signal. Note that the symbols A-N and P on the lines connecting each component device are used to explain the operation later.

In FIG. 3, the turbine speed signal A is compared with the speed setting signal B in an adder 1, and the deviation signal C is amplified in an amplifier 2 having a gain commensurate with the steam control valve regulation rate.
The output signal RI and the load setting signal F are added by an adder 3 to form a steam control valve flow rate request signal E. Further, the speed deviation signal C is amplified by an amplifier 4 having a gain commensurate with the in-winter valve regulation rate, and the output signal H thereof and the load setting signal G of the intercept valve corresponding to the load setting determined by the amplifier 5 are amplified. are added by adder 6.

This becomes the intercept valve flow signal I.

On the other hand, the reactor pressure signal J is converted into a pressure setting signal by an adder 8.
The difference signal is amplified by an amplifier 9 having a gain commensurate with the pressure adjustment rate, and becomes a steam flow rate signal M of the steam generated from the JM sub-reactor.

The respective signals E, M determined by the speed/load control circuit and the pressure control circuit are compared by a low value priority circuit 7 and only the low value signal is passed and the steam regulator flow signal N
becomes. Further, in an adder 1°, the steam control valve flow rate signal N is subtracted from the steam flow rate signal M generated from the nuclear reactor to obtain a turbine bypass valve flow rate signal P.

In order to improve the reliability of power supply as the proportion of nuclear power generation in the power system increases, steam turbines with a control device configured as described above do not easily scram due to certain frequency fluctuations. No particular consideration was given to continuing operation.

[Problem that the invention seeks to solve]

In a power generation steam turbine equipped with a control system configured as described above, when a large-scale load drop occurs in the power system, the turbine speed increases as the system frequency increases, so the steam control valve is The steam regulator valve closes to an opening corresponding to the steam regulator flow rate request signal determined by the regulation rate, thereby preventing overspeed of the turbine. At the same time, the turbine bypass valve
The turbine bypass valve is opened to an opening corresponding to the turbine bypass valve flow rate signal obtained by subtracting the steam control valve flow rate request signal from the reactor generated steam flow scene signal, and the excess steam due to the steam control valve being closed is sent to the condenser. However, in plants with partial capacity turbine bypass valves, if the steam moderation valve is closed above the turbine bypass valve capacity, the reactor pressure will rise and eventually lead to a high neutron flux scram - for example, 25 The case of frequency increase in a steam turbine of a boiling water atomic coupler with a % capacity turbine bypass valve will be explained with reference to FIG.

The rated frequency of the system is 5. When the system frequency rises to 50.25 Hz ■, the steam control valve begins to close ■, and when it increases to 50.88 H2O, the steam control valve closes until it reaches the capacity of the turbine bypass valve (100% - 25% = 75% ■). Closed, the turbine bypass valve becomes fully open.As the frequency increases further, the steam control valve closes more than the turbine bypass valve capacity, resulting in a reactor scram.

The purpose of the present invention is to expand the limit of increase in system frequency in order to improve the ability of a plant having a partial capacity turbine bypass valve to withstand system frequency disturbances, so that it is possible to continue operation without easily scramming in response to an increase in system frequency. The object of the present invention is to provide a turbine control device that is possible.

[Means for solving problems]

The above purpose is to maintain the steam regulator speed regulation rate at the bypass valve capacity position in a certain frequency range and prevent the steam regulator valve from closing when the system frequency increases. This is achieved by giving the constant rate nonlinear characteristics.

As a concrete configuration for applying the above-mentioned principle in practical terms,
The control device according to the present invention includes (a) a speed/load control circuit that receives a turbine speed signal, a turbine speed setting signal, and a load setting signal and outputs an intercept riser ia, and (b) a steam A pressure control circuit that generates a steam flow rate signal in response to a pressure signal and a pressure setting signal, and (Q) comparing the output signal of the speed/load control circuit with the output signal of the pressure control circuit, (d) a low value priority circuit that outputs a steam control valve flow rate signal by passing only the value signal; and (d) a turbine bypass valve flow signal that is obtained by subtracting the output signal of the low value priority circuit from the output signal of the pressure control circuit. The present invention is applied to a turbine control device equipped with an output adder, and is provided with a function generator that gives nonlinear characteristics to the speed deviation signal of the speed/load control circuit.

[Effect]

An example of the speed regulation function of a steam regulating valve that is given nonlinear characteristics by the control device configured as described above is explained with reference to FIG. 5. In this example, when the system frequency rises to 50.25 Hz, the steam regulating valve closes. Beginning■, 50.88 Hz
When the steam temperature rises to , the steam control valve closes until it reaches the capacity of the turbine bypass valve, and the turbine bypass valve becomes fully open. When the system frequency is in the range from 50.88 Hz to 51.5 Hz, the steam control valve opening is maintained at a position corresponding to the turbine bypass valve capacity. As the frequency further increases, the steam control valve begins to close beyond the turbine bypass valve capacity θ, and the reactor reaches a scram.

In other words, by making the steam control valve speed adjustment rate non-linear as shown in Figure 5, if the turbine bypass valve capacity is the same, the system frequency increase limit that does not lead to reactor scram can be changed from 50.88Hz to 51.5Hz. It becomes possible to raise it.

The above-mentioned frequency values are merely examples, and the present invention is not limited to these values when implementing the present invention.

FIG. 6 shows the relationship between the frequency rise of the steam regulator and intercept valve and the opening request signal when the steam regulator valve speed regulation rate is made non-linear.

In order to prevent the intermediate steam pressure from rising, the intercept valve begins to close after the steam regulating valve opening request signal becomes zero, but at partial load (1), for example, when the load setting is 60%, the steam regulating valve opening request signal The intercept valve begins to close before becomes zero.

For this reason, it is necessary to make the intercept valve control signal non-linear at the same time as making the steam regulator speed regulation rate non-linear, so that the intercept valve starts closing only after the steam regulator valve opening request signal becomes zero. Therefore, the speed regulation rate of the steam control valve and the intercept valve is made nonlinear by adding a nonlinear element to the turbine speed deviation signal.

On the other hand, due to the nonlinearization of the speed regulation rate, the amount of steam flowing into the steam turbine increases during load shedding, so the maximum speed increase rate of the steam turbine increases, but care must be taken to prevent the steam turbine from overspeed tripping. No, 40
% output or more, the steam control valve and intercept valve close suddenly, so there is no problem, but 40
When the load is cut off below % output, the steam regulating valve temporarily maintains its opening state, so when the steam regulating valve is fully closed, the intermediate steam pressure can become less than the equivalent of 15% output of the intercept valve sudden closing condition. There is sex. In this state, the intercept valve does not close quickly and the turbine trips overspeed. Therefore, at an output of 40% or less, the conventional linear adjustment rate is used.

To determine whether the output is 40% or less, a reactor-generated steam flow rate signal that does not change due to an increase in frequency is used.

1 An embodiment of the present invention will be explained below with reference to FIG. 1.0 FIG. 1 is a diagram showing the configuration of a control device of the present invention, and in contrast to the conventional device shown in FIG. This is a configuration with the addition of . That is, a function generator 11 for nonlinearizing the speed regulation rate, and a determiner 13 for determining output 40% from the reactor generated steam flow rate signal. It has a configuration in which a switch 14 for changing the speed adjustment rate and an adder 12 are added.

The determiner 13 turns on the changeover switch 14 when the reactor generated steam flow rate signal M becomes equal to or more than 40% of the turbine output.
The output signal Q from the function generator 11 corresponding to the speed deviation signal C is applied to the adder 12. The adder 12 receives the signal Q from the function generator 11 and the speed deviation signal C, and outputs a nonlinearized speed deviation signal R.

FIG. 7 shows the states of the output signal Q from the function generator and the output signal R from the adder 12 corresponding to the speed deviation signal C1 in the control device according to the present invention when the system frequency increases. The signal R is determined when the switch 14 is switched in the determiner 13, that is, when the output is 40% or more (signal Rz) and when the output is 40% or less (signal R1).
It shows both.

When the output is 40% or more, the nonlinear signal Rz is obtained by subtracting the output signal Q of the function generator 11 from the conventional linear p output signal R1 when the output is 40% or less.

For example, when the output is 40% or more, the signal R2 is amplified by the amplifier 2 having a gain that takes into account the adjustment rate of the steam control valve, resulting in a nonlinear output signal Dz as shown in FIG. The load setting is added to this signal Da by an adder 3.

A nonlinear steam control valve flow rate request signal E is output.

Further, when the output is 40% or less, the output signal of the amplifier 2 becomes the same linear output signal D1 as the conventional one, and the steam control valve flow rate request signal E becomes a linear signal.

As described above, by providing a function generator in the turbine speed deviation signal circuit and making the speed deviation signal nonlinear, the steam control valve flow rate request signal becomes a nonlinear signal, and the steam control valve opening is maintained within a certain frequency range. It became possible to do so. In addition, when the output is 40% or less, the linear characteristic is maintained as before, thereby preventing overspeed trip when the load is cut off at the output 40% or less.

〔Effect of the invention〕

As detailed above, according to the control device of the present invention, a nuclear reactor that drives a steam turbine plant equipped with a partial capacity bypass can be easily operated in response to a certain frequency increase in the power system due to load drop, etc. without scrumming,
This will make it possible for the plant to continue operating, and will greatly contribute to improving the reliability of the power supply from nuclear power generation.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram showing an embodiment of the control device of the present invention. Fig. 2 is a steam system diagram of the turbine, Fig. 3 is a system diagram showing the configuration of a conventional turbine control device, Fig. 4 is a chart showing the conventional steam control valve speed regulation rate, and Fig. 5 is a diagram showing the present invention. Chart showing the steam regulating valve speed regulation rate with nonlinear characteristics,
FIG. 6 is a chart showing the relationship between frequency and the opening degree of the steam control valve and the intercept valve. FIGS. 7 and 8 are charts for explaining the functions and effects of the embodiment shown in FIG. 1. 1.3,6,8,10,12...Adder, 2,4゜5
．． 9...Amplification hot water, 7...Low value priority circuit, 11...
Function generation tree, 13...determiner, 14...switch,
101... Nuclear reactor, 102... Turbine bypass valve, 103... Main steam stop valve, 104... Steam control valve, 105... High pressure turbine, 106a, 106b...
・Moisture separator, 107 a to 107 f-... Intermediate steam stop valve, 108 a to 108 f intercept valve, 10
9a to 109c...low pressure turbine, 110...
Generator, 111... Condenser, 112... Water supply pump, 113... Main circuit breaker.

Claims (1)

[Claims] 1. (a) A speed/load control circuit that receives a turbine speed signal, a turbine speed setting signal, and a load setting signal and outputs an intercept valve flow signal; (b) steam pressure; (c) comparing the output signal of said speed/load control circuit with the output signal of said pressure control circuit; (d) a low value priority circuit that outputs a steam control valve flow rate signal by passing only the signal; and (d) an output signal of the low value priority circuit is subtracted from the output signal of the pressure control circuit to output a turbine bypass valve flow rate signal. What is claimed is: 1. A turbine control device comprising: an adder for adding non-linear characteristics to the speed deviation signal of the speed/load control circuit; 2. The function generator is provided with a changeover switch and a determiner that operates the changeover switch, and the determiner determines the load state of the turbine based on the output signal of the pressure control circuit. The changeover switch determines the nonlinear characteristics of the function generator as speed/speed.
A turbine control device having nonlinear characteristics according to claim 1, wherein the turbine control device switches between a state in which the speed deviation signal of the load control circuit is added and a state in which it is not added.