JP2511009B2 - Turbin controller having non-linear characteristics - Google Patents

Description

The present invention relates to a control device for a steam turbine, and more particularly to a control device suitable for a power generation steam turbine provided with a partial capacity turbine bypass valve.

[Conventional technology]

Generally, a turbine for driving a generator (for example, a steam turbine combined with a boiling water reactor) is normally operated at a speed adapted to the frequency of the electric power system, but a large load is applied to the electric power system. In the case where a dropout occurs, there is a risk that the system frequency will rise due to excessive rotation of the turbine. In a boiling water nuclear plant with a partial capacity turbine bypass valve, when the system frequency rises, the steam control valve is closed according to the speed regulation rate to prevent overspeed of the turbine, and at the same time the turbine bypass valve opens and excess steam is removed. It is sent to the condenser. When the frequency rises significantly and the closing amount of the steam control valve exceeds the turbine bypass valve capacity,
Reactor pressure rises, eventually leading to neutron flux high scrum. The percentage of nuclear power plants in the electric power system is increasing these days, and it is necessary to be able to continue operation of the plant without scramming easily for a certain system frequency fluctuation.

Regarding the control of this type of turbine, the technology of Japanese Examined Patent Publication No. Sho 60-32002 is known.

FIG. 2 is a steam system diagram of a steam turbine in a boiling water nuclear power plant.

The steam emitted from the nuclear power 101 flows through the main steam stop valve 103 and the steam control valve 104 into the high pressure turbine 105. The steam leaving the high-pressure turbine 105 passes through the moisture separators 106a and 106b, the intermediate steam stop valves 107a to 107f, and the intercept valves 108a to 108f.
Through the low pressure turbines 109a to 109c, and the respective exhaust gases are guided to the condenser 111. The water condensed by the condenser 111 is returned to the reactor 101 again by the reactor water supply pump 112. When the amount of steam generated from the nuclear reactor is larger than the steam flow rate required by the turbine, surplus steam is directly flown to the condenser 111 through the turbine bypass valve 102. A generator 110 driven by a steam turbine is connected to a power system via a main circuit breaker 113.

FIG. 3 is a control system diagram showing a configuration of a known technique relating to a control device for a steam turbine of a boiling water plant, in which FIG.
Is an adder that calculates the deviation between the turbine speed signal obtained by detecting the rotational speed of the turbine and the speed setting signal that sets the turbine speed. Reference numeral 2 is an amplifier, 3 is an adder, and the output of the amplifier 2 and a load setting signal are given to extract a steam regulating valve flow rate request signal.

An adder 6 is provided with 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 to extract the intercept valve flow rate signal. A speed / load control circuit is configured by the above-mentioned components (1 to 6). 8 is an adder, which is a pressure signal obtained by detecting the pressure of steam generated from the reactor,
And a pressure setting signal that sets the pressure of the steam. 9
Is an amplifier, and these components (8, 9) form a pressure control circuit. Reference numeral 7 is a low value priority circuit, which compares the steam control valve flow rate request signal from the speed / load control circuit with the output signal of the pressure control circuit, and passes only the low value signal with priority to pass the steam control valve flow rate. Extract the signal. An adder 10 is provided 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. The symbols A to N, P on the lines connecting the respective components are for explaining the operation later.

In FIG. 3, the turbine speed signal A is compared with the speed setting signal B by the adder 1, and the deviation signal C thereof is amplified by the amplifier 2 having a gain commensurate with the steam control valve adjustment rate, and its output signal D is obtained. The load setting signal F and the load setting signal F are added by the adder 3 to become the steam control valve flow rate request signal E. The speed deviation signal C is amplified by the amplifier 4 having a gain commensurate with the intercept valve regulation rate, and its output signal H and the load setting signal G of the intercept valve corresponding to the load setting obtained by the amplifier 5 are added together. 6 is added to form the intercept valve flow rate signal I.

On the other hand, the reactor pressure signal J is compared with the pressure setting signal K by the adder 8, and the deviation signal L thereof is amplified by the amplifier 9 having a gain commensurate with the pressure regulation rate, and the steam generated from the reactor is It becomes the vapor flow rate signal M.

The respective signals E and M obtained by the speed / load control circuit and the pressure control circuit are compared by the low value priority circuit 7, only the low value signal passes, and the steam control valve flow rate signal N
Becomes Further, in the adder 10, the steam control valve flow signal N is subtracted from the steam flow signal M generated from the nuclear reactor to obtain a turbine bypass valve flow signal P.

In the steam turbine having the control device configured as described above, in order to improve the reliability of the power supply with the increase in the ratio of nuclear power generation in the power system, it is possible to easily scram to a certain frequency fluctuation. No special consideration is given to continuing operation.

[Problems to be solved by the invention]

The steam turbine for power generation with the control system configured as described above uses a steam control valve because the turbine speed increases as the frequency of the system increases when a large load drop occurs in the power system. The steam control valve is closed to an opening degree corresponding to the steam control valve flow rate request signal determined by the adjustment rate to prevent overspeed of the turbine. At the same time, 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 rate signal, and excess steam due to the steam control valve being closed. To the condenser. However, in a plant having a partial capacity turbine bypass valve, when the steam control valve is closed more than the turbine bypass valve capacity, the reactor pressure rises and eventually a neutron flux high scrum is reached. As an example, a case of frequency increase in a steam turbine of a boiling water nuclear power plant having a 25% capacity turbine bypass valve will be described with reference to FIG.

If the rated frequency of the grid is 50Hz, the grid frequency is 5
When increasing to 0.25Hz, the steam control valve begins to close.
When it increases to 0.88Hz, the steam control valve closes to the turbine bypass valve capacity equivalent (100% -25% = 75%) and the turbine bypass valve is fully opened.When the frequency further increases, steam control valve exceeds the turbine bypass valve capacity. Reach the reactor scrum to close the valve.

An object of the present invention is to improve resistance to system frequency disturbance of a plant having a partial capacity turbine bypass valve,
An object of the present invention is to provide a turbine control device capable of continuing the operation by expanding the system frequency increase limit, not easily scramming against the system frequency increase.

[Means for solving problems]

The purpose of the above is to keep the steam control valve speed regulation rate at a position of the bypass valve capacity in a certain frequency range and prevent the control valve from closing when the system frequency increases, that is, the steam control valve speed control. This is achieved by having a non-linear characteristic in the constant rate.

As a specific configuration for applying the above principle to practical use, the control device according to the present invention is provided with (a) a turbine speed signal, a turbine speed setting signal, and a load setting signal. A speed / load control circuit that outputs a signal, and (b) a pressure control circuit that receives a steam pressure signal and a pressure setting signal to generate a steam flow signal,
(C) A low-value priority circuit that compares the output signal of the speed / load control circuit with the output signal of the pressure control circuit and passes only the low-value signal to output the steam control valve flow rate signal,
(D) is applied to a turbine control device including an adder that subtracts the output signal of the low value priority circuit from the output signal of the pressure control circuit and outputs a turbine bypass valve flow rate signal,
A function generator for providing a non-linear characteristic to the speed deviation signal of the speed / load control circuit is provided.

[Action]

An example of the speed adjusting function of the steam control valve to which the non-linear characteristic is given by the control device configured as described above will be described with reference to FIG. In this example, when the system frequency rises to 50.25Hz, the steam control valve begins to close, and when it rises to 50.88Hz, the steam control valve closes to the turbine bypass valve capacity.
D, Turbine bypass valve is fully opened. System frequency is 5
In the range of 0.88Hz to 51.5Hz, the characteristics are such that the steam control valve opening and the turbine bypass valve capacity are maintained at the corresponding positions. When the frequency further increased, the steam control valve began to close more than the turbine bypass valve capacity, and the reactor reached scram.

That is, by making the steam control valve speed adjustment rate non-linear as shown in Fig. 5, the system frequency increase limit that does not reach the reactor scram is increased from 50.88Hz to 51.5Hz if the turbine bypass valve capacity is the same. It becomes possible.

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

FIG. 6 shows the relationship between the frequency increase of the steam control valve and the intercept valve and the opening degree request signal when the steam control valve speed adjustment rate is made non-linear. Normally, the intercept valve starts to close after the steam control valve opening request signal reaches zero in order to prevent the intermediate steam pressure from rising, but at partial load,
For example, when the load setting is 60%, the intercept valve starts to close before the steam control valve opening request signal 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 control valve speed adjustment rate non-linear so that the intercept valve starts to close after the steam control valve airiness demand signal becomes zero. Therefore, the speed adjustment rate of the steam control valve and the intercept valve is made non-linear by inserting a non-linear element in the turbine speed deviation signal.

On the other hand, when the load is cut off,
Since the amount of steam flowing into the steam turbine increases, the maximum speed increase rate of the steam turbine increases, but it must be taken into consideration so that the steam turbine does not trip overspeed. 40
When the load is cut off above the% output, the steam control valve will close rapidly and the intercept valve will close rapidly.
When the load is cut off below the% output, the steam control valve will continue to hold the opening halfway, so the intermediate steam pressure can be less than 15% of the intercept valve rapid closing condition when the steam control valve is fully closed. There is a nature. In this condition, the intercept valve does not close rapidly and the turbine overspeed trips. Therefore, when the output is 40% or less, the conventional linear adjustment rate is used. The 40% or less power output uses the reactor generated steam flow signal, which does not change with increasing frequency.

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a diagram showing a configuration of a control device of the present invention, which is a configuration in which a portion Pat surrounded by a chain line is added to the conventional device shown in FIG. That is, the function generator 11 for making the speed regulation rate non-linear, output 40% from the reactor generated steam flow signal
Judgment device 13 for determining the speed, switch for switching the speed adjustment rate
14 and an adder 12 are added.

The determination unit 13 outputs the turbine generated steam flow signal M to the turbine output.
When it reaches 40% or more, turn on the changeover switch 14,
Output signal Q from the function generator 11 according to the speed deviation signal C
Is given to the adder 12. The adder 12 receives the signal Q of the function generator 11 and the speed deviation signal C, and outputs a non-linearized speed deviation signal R.

FIG. 7 shows the states of the speed deviation signal C, the output signal Q from the function generator corresponding to the speed deviation signal C, and the output signal R from the adder 12 in the control device according to the present invention when the system frequency rises. The signal R indicates both when the switch 14 is switched by the determiner 13, that is, when the output is 40% or more (signal R ₂ ) and when the output is 40% or less (signal R ₁ ).

When the output is 40% or more, the output signal Q of the function generator 11 is subtracted from the conventional linear output signal R ₁ when the output is 40% or less to obtain a nonlinear signal R ₂ .

For example, when the output is 40% or more, the signal R ₂ is an amplifier 2 having a gain in consideration of the adjustment rate of the steam control valve.
A non-linear output signal D ₂ as shown in FIG.
Becomes The load setting is added to the signal D ₂ by the adder 3, and a nonlinear steam reduction 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 D ₁ 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 non-linear, the steam control valve flow rate request signal becomes a non-linear signal, and the steam control valve opening degree is maintained within a certain frequency range. It was possible to do so.
When the output is 40% or less, the linear characteristic is used as before to prevent the overspeed trip at the time of load shedding of the output 40% or less.

〔The invention's effect〕

As described above in detail, according to the control device of the present invention, a reactor for driving a steam turbine plant equipped with a partial capacity bypass can be easily provided against a constant frequency increase in the system due to load drop in the power system. This makes it possible to continue operating the plant without scramming, which greatly contributes to improving the reliability of the power supply by nuclear power generation.

[Brief description of drawings]

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 a turbine, FIG. 3 is a system diagram showing a configuration of a conventional turbine control device, FIG. 4 is a table showing a conventional steam control valve speed adjustment rate, and FIG. 5 is according to the present invention. FIG. 6 is a chart showing a steam control valve speed adjustment rate having a non-linear characteristic, and FIG. 6 is a chart showing a relationship between frequency and steam control valve and intercept valve opening. FIG. 7 and FIG. 8 are charts for explaining the action and effect in the embodiment shown in FIG. 1,3,6,8,10,1
2 ... Adder, 2,4,5,9 ... Amplifier, 7 ... Low value priority circuit, 11 ... Function generator, 13 ... Judger, 14 ... Switch, 101 ... Reactor, 102 ...... Turbine bypass valve, 103
...... Main steam stop valve, 104 …… Steam control valve, 105 …… High pressure turbine, 106a, 106b …… Moisture separator, 107a to 107f …… Intermediate steam stop valve, 108a to 108f Intercept valve, 109a to 10
9c …… Low pressure turbine, 110 …… Generator, 111 …… Condenser,
112 …… Water supply pump, 113 …… Main circuit breaker.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidezumi Kuwashima 3-1-1, Sachimachi, Hitachi City Hitachi factory, Hitachi Ltd. (72) Takumi Kawai 5-2-1, Omikacho, Hitachi City Stock company Hitachi Ltd. Omika factory

Claims (1)

(57) [Claims] 1. A speed / load control circuit which outputs an intercept valve flow rate signal when (a) a turbine speed signal, a turbine speed setting signal and a load setting signal are given,
(B) A pressure control circuit that receives a steam pressure signal and a pressure setting signal to generate a steam flow signal, and (c) compares the output signal of the speed / load control circuit with the output signal of the pressure control circuit. Then, the low value priority circuit that outputs only the low value signal and outputs the steam control valve flow rate signal, and (d) the output signal of the low value priority circuit is subtracted from the output signal of the pressure control circuit, and the turbine bypass A turbine controller having an adder which outputs a valve flow rate signal, wherein a turbine generator having a non-linear characteristic is provided with a function generator for giving a non-linear characteristic to a speed deviation signal of the speed / load control circuit. apparatus.