JPH0758042B2 - Intercept valve rapid closing control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a turbine interception valve abrupt closing control device, and particularly to a stable plant for a (steam) turbine generator used in a system with large load fluctuations. The present invention relates to an intercept valve rapid closing control device suitable for realizing operation.

[Conventional technology]

As the installation location of the power plant moves away from the power consumption area, the need for so-called partial load cutoff operation, which shifts from full load operation to operation sharing only the load of the power plant area due to system accidents, etc., increases. I'm doing it. In such a partial load operation, the intercept valve abrupt closing operation is required for the turbine overspeed prevention control due to the abrupt reduction of the turbine load.

In order to meet this requirement, conventionally, as a turbine overspeed prevention circuit at the time of load cutoff, etc., an intercept valve that detects turbine acceleration or an intercept valve closing command and suddenly closes the intercept valve when these are above a certain value There is a quick valve closing control device. (See Japanese Patent Laid-Open No. 60-175710) In such a conventional device, since the operating condition of the device is determined by using only the turbine speed or its function value as a parameter, the intercept valve can be opened and closed quickly such as when the partial load is cut off. When the operation is required, the intercept valve is suddenly closed again, which has a drawback that the stable operation of the plant is disturbed. This will be specifically described below.

FIG. 2 shows a system diagram of a reheating turbine which is a turbine of a general generator.

The steam generated in the boiler 1 is guided from the superheater 17 to the main steam pipe 2, passes through the regulator valve 3, and causes the high-pressure turbine 4 to generate torque. The steam discharged from the high-pressure turbine 4 returns to the boiler 1 again and is heated again by the reheater 5. The reheated steam is guided to the reheated steam pipe 6 and intercepted by the intercept valve 7
Through the low pressure turbine 8 to generate torque there.

The high-pressure turbine 4 and the low-pressure turbine 8 drive a generator 9 to generate electric power.

The steam emitted from the low-pressure turbine 8 is condensed into water by the condenser 10 and is sent to the boiler 1 again through the condensate pump 11, the low-pressure heater 12, the water absorption pump 13, the high-pressure heater 14, and the like.

The water sent to the boiler 1 is heated by the water wall 15 of the furnace to generate steam. The generated steam is further heated by a superheater 17 from a drum (in the case of a drum boiler) 16 and sent out from the boiler to the main steam pipe 2.

An electro-hydraulic type governor is generally used for load and speed control of such a turbine generator, and FIG. 3 shows an outline of the control system.

The rotation speed of the turbine generator 9 must always be constant, and the turbine rated rotation speed R is set. However, since the load on the turbine generator 9 increases or decreases due to the increase or decrease in the power demand, the actual turbine rotation speed F at the present time changes every moment.

From these two rotation speeds R and F, adders 19 and 21 and multipliers
Using 20, the set point C, which is the turbine generator output value that should be generated at the present moment, is calculated by the following equation (1).

C = L + (R−F) × D (1) where L is a basic turbine output set value,
D is a speed regulation rate. When the demand for electric power decreases and the load on the turbine generator 9 decreases, the actual turbine rotation speed F increases.

Then, the value of the difference (R−F) obtained by subtracting the actual turbine rotation speed F from the turbine rated rotation speed R becomes negative, and the output is lowered by (R−F) D from the basic turbine output measurement value L. The value becomes the set point C.

As shown in FIG. 4, the opening characteristic of the regulating valve 3 and the intercept valve 7 with respect to the set point C is such that the opening degree of the regulating valve 3 decreases as the set point decreases, and Each opening generator or cam characteristic 2 so that the intercept valve 7 starts to close after it is fully closed.
2,23 is set.

From the equation (1), when the output set value L is constant, the set point C is a function of the rotational speed deviation (R−F), and thus the (R−F) is used as a variable to obtain the set point C. When the opening command value of each valve with respect to this set point C is obtained from FIG. 4, the above (R-
F) That is, the opening command value of each valve can be obtained as a function of the rotation speed increase rate.

As an example, assuming that the basic output setting value L is a constant value of 50%,
As described above, when FIG. 4 is rewritten as the deviation of the actual rotation speed F from the rated rotation speed R on the horizontal axis, that is, the rotation speed increase rate, it becomes as shown in FIG. In the figure, a straight line 3LD is an adjustment valve opening command value (characteristic), and a straight line 7LD is an intercept valve opening command value (characteristic).

From Fig. 5, when the turbine rotation speed increases, the control valve opening / closing command starts to gradually decrease from 50%, and the rotation speed becomes D / 2.
It will be understood that when it reaches 0%, it becomes 0, and when the turbine speed further increases, the opening command value of the intercept valve decreases, and the valve tries to close.

The intercept valve abrupt closing circuit 24 in FIG. 3 judges the condition of the intercept valve closing operation, and when the above condition is satisfied, an intercept valve abrupt closing command is generated and the valve is abruptly closed by an appropriate hydraulic mechanism. It is what makes me.

That is, the intercept valve opening command and the intercept valve actual opening signal, which are the outputs of the function generator 23, are subtracted by the subtractor 24D.
To the comparator 24C. When the difference output becomes less than or equal to a negative expected value (for example, 5%),
The comparator 24C determines that the turbine is overspeed and generates an intercept valve abrupt closing signal.

The subtractor 26 detects a deviation of the actual opening of the intercept valve from a target value, and generates an intercept valve control signal according to the deviation, which constitutes a known intercept valve opening control system. .

The intercept valve abrupt closing signal is supplied to the intercept valve abrupt closing means 25, whereby the intercept valve 7 is rapidly driven to the fully closed state.

Now, FIG. 6 shows the operation when a partial load interruption occurs in such an operating state.

When the partial load interruption occurs at time T ₀ , the turbine inflow energy and the output energy are out of balance, so that the turbine rotation speed, that is, the rotation speed increases.

When the rotation speed increase rate reaches D / 2 or more at time T ₁ , the intercept valve abrupt closing circuit 24 outputs the abrupt closing signal. This rapid closing signal is supplied to the intercept valve rapid closing means 25,
This causes the intercept valve 7 to close rapidly.

Therefore, while the amount of steam flowing into the low-pressure turbine 8 is rapidly reduced, the rotational energy of this turbine is generated by the generator 9
Is converted to electrical energy at the turbine 8
The number of revolutions drops rapidly. Due to such a decrease in the rotation speed of the turbine 8, the intercept valve command changes to the opening direction, and the valve is rapidly driven in the opening direction.

At this time, since the steam source in the reheater 5 still has energy equivalent to the high load before the partial load cutoff, the amount of steam flowing into the low pressure turbine 8 increases with the opening operation of the intercept valve 7. Then, the number of revolutions rises rapidly again.

Therefore, the intercept valve rapid closing circuit 24 is re-operated, the intercept valve 7 is closed, and the rotational speed of the turbine 8 is reduced again. Repeated rapid closing and rapid opening of the intercept valve in this manner may lead to a dangerous state.

[Problems to be solved by the invention]

As described above, in the conventional intercept valve rapid closing device,
If the intercept valve is required to be opened immediately after the intercept valve is closed suddenly, such as when the partial load is cut off, the intercept valve rapid closing device will re-operate. There is a problem that the plant cannot be expected to operate stably after repeated opening.

The object of the present invention is to detect the state of the intercept valve,
It is an object of the present invention to provide an interception valve abrupt closing control device capable of continuing stable operation of a plant by preventing unnecessary re-abrupt closing operation of the interception valve after a partial load cutoff.

[Means for solving problems]

In the present invention, attention is paid to the turbine speed control range after the intercept valve is closed until the intercept valve is fully opened again. In this control range, the intercept valve is closed as a turbine overspeed prevention function. By prohibiting the re-operation of the equipment, the turbine speed is settled, and stable regional load operation can be continued thereafter.

[Action]

After the intercept valve is closed abruptly, as described above, the turbine speed decreases, so the intercept valve open signal is output, and as a result, the turbine speed rises and the intercept valve tries to close rapidly again. According to the invention, after the intercept valve is once closed, the intercept valve is prevented from being closed suddenly until the intercept valve reaches the fully opened state. Although the responsiveness of is somewhat slower, it is almost completely prevented that the partial load operation becomes unstable due to repeated closing and opening of the intercept valve.

〔Example〕

One embodiment of the present invention will be described with reference to the block diagram of FIG. 1A and the waveform diagram of FIG. Here, an example is given in which a partial load cutoff occurs on the system side at time T ₀ during rated load operation, and the operation shifts to 50% load operation.

In the block diagram of FIG. 1 (a), the same parts as those of FIG. 3 such as the intercept valve abrupt closing circuit are denoted by the same reference numerals and the description thereof will be omitted.

In the steady operation state, the intercept valve abrupt closing circuit 24 of FIG. 1 (a) does not generate an output (judgment) signal.
The output of the first inverting circuit 24A becomes high level and the first flip-flop 24B is in the reset state. That is, the intercept valve abrupt closing command that is the output thereof is not generated.

On the other hand, since the intercept valve 7 is fully opened, the second flip-flop 24F is also reset, the output of the second inverting circuit 24G becomes high level, and the AND gate 24E is opened. However, in this state, the output of the AND gate 24E becomes low level.

Immediately after the load is cut off at time T ₀ , the balance between the steam energy flowing into the turbine and the load energy is lost, and the reduced load energy is converted into the rotational energy of the turbine, so the turbine speed increases rapidly. To do.

Therefore, where the rotational speed exceeds D12, at time T ₁ of the other words Fig. 1 (b), the intercept valve suddenly closed circuit 24 determines the turbine overspeed, to generate an output signal.

As described above, since the AND gate 24E is opened by the output of the second inverting circuit 24G at this time, the output (judgment) signal is input to the first flip-flop 24B via the AND circuit 24E, set.

As a result, the intercept valve rapid closing command is generated, the intercept valve rapid closing means 25 is activated, and the intercept valve 7 is closed.
Is abruptly closed, so it is possible to suppress an increase in the rotational speed of the turbine 8. In this way, excessive speed increases of the turbine 8 are prevented.

At this time, since the second flip-flop 24F is set in response to the intercept valve abrupt closing command, the output of the second inverting circuit 24G becomes low level, and the AND gate 24E
Is closed.

By rapidly closing the intercept valve 7, the inflow steam to the low-pressure turbine 8 is cut off, and the turbine inflow energy becomes smaller than the load energy. As a result, the turbine speed decreases and the output of the intercept valve rapid closing circuit 24 disappears.

As a result, the output of the first inverting circuit 24A becomes high level, the first flip-flop 24B is reset, and the intercept valve abrupt closing command disappears. At this time, since the second flip-flop 24F is not affected and is kept in the set state, the AND gate 24E is also closed.

When the turbine speed falls below the predetermined value, the intercept valve 7 starts to open again as shown in FIGS. 5 and 3, and the turbine speed starts to increase. When the turbine speed exceeds D / 2, as described above, the intercept valve abrupt closing circuit 24 determines that the turbine is overspeed and generates an output signal.

However, at this time, as described above, the second inverting circuit 24G
Is low level and the AND gate 24E is closed, the state of the first flip-flop 24B does not change, and the intercept valve abrupt closing command is not generated.

The function of blocking the intercept valve abruptly closing command continues until the intercept valve is fully opened thereafter and the detection signal thereof is generated.

That is, after the intercept valve 7 is suddenly closed by the first intercept valve rapid closing command, the intercept valve is opened again by the normal intercept valve opening control system (the system of the subtractor 26 in FIG. 3) to rotate the turbine. Even if the number increases, according to the present invention, the re-quick closing operation is prohibited until the intercept valve 7 reaches full opening again after the intercept valve is closed rapidly.

Therefore, from the second time onward-in other words, in FIG. 1 (b),
The suppression of the speed increase after time T ₁ is not performed by the sudden closing control of the intercept valve 7, but only by the normal intercept valve opening control system (the system of the subtractor 26 in FIG. 3).

Therefore, the speed control for the turbine speed increase after the second time becomes slightly slower, but the steam energy stored in the reheat steam chamber is converted to the load energy,
The turbine speed rapidly decreases, and the turbine speed increase after the second time becomes slight. Eventually, the intercept valve fully opens and the turbine speed stabilizes.

When the intercept valve is fully opened and the full open signal is generated, the flip-flop 24F is reset and its output becomes low level, so the output of the second inverting circuit 24G becomes high level and the AND gate 24E is opened. , Return to the initial or steady state before the intercept valve command was issued.

As is apparent from the above description, the first and second inverting circuits 24A and 24G and the first and second flip-flops 24B and 24 shown in FIG.
In F and AND gate 24E, the (overspeed) determination output of the intercept valve rapid closing circuit 24 is the intercept valve rapid closing means 25.
Means for prohibiting rapid closing operation to prevent the supply of
Are configured.

According to the present embodiment, the intercept valve abrupt closing circuit operates due to the partial load cutoff and the like, and after the intercept valve is abruptly closed, the opening (or position) of the intercept valve is detected and this is fully opened. By preventing the re-quick closing operation until it reaches the limit, the harmful interception valve rapid closing operation after the load is blocked is suppressed, and the normal opening based on the deviation of the detected actual opening from the intercept valve opening command is performed. Since the opening degree or the position of the intercept valve is controlled by the closed loop control of, stable plant operation can be continued.

In the above, the conventional intercept valve rapid closing circuit 24 is left as it is, and each logic element shown by reference numerals 24A, 24B, 24E to 24G in FIG. A speed determination output, that is, an example in which a conventional intercept valve abrupt closing command is configured to be prevented from being supplied to the intercept valve abrupt closing means 25 has been described. As a matter of course, the control itself may be prevented from being generated, or the operation of the intercept valve abrupt closing means may be blocked.

For that purpose, for example, in FIG. 3, the operations of the subtracter 24D and the comparator 24C may be suppressed, or a predetermined specific input / output may be forcibly generated.

〔The invention's effect〕

According to the present invention, when the intercept valve has to be opened immediately after the intercept valve is suddenly closed, such as when a partial load is shut off, it is possible to prevent re-operation of the intercept valve rapid closing device, thus ensuring plant safety. You can continue driving.

[Brief description of drawings]

1 (a) is a block diagram showing an essential part of an embodiment of the present invention, FIG. 1 (b) is a time chart showing its operation, FIG. 2 is a system diagram of a general reheat steam turbine, FIG. 3 is a block diagram showing a control system of the regulator valve and the intercept valve of FIG. 2, FIG. 4 is a diagram showing an example of valve opening characteristic with respect to an output command, and FIG. 5 is a diagram showing rotation speed deviation, that is, rotation speed increase rate. FIG. 6 is a diagram showing an example of the valve opening characteristic, and FIG. 6 is a time chart for explaining control by the conventional method when partial load interruption occurs. 1 ... Boiler, 3 ... Regulator, 4 ... High-pressure turbine, 5
...... Reheater, 7 …… Intercept valve, 8 …… Low pressure turbine, 24 …… Intercept valve rapid closing circuit, 25 …… Intercept valve rapid closing means, 27 …… Abrupt closing operation prohibiting means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideaki Kaneda, Hideaki Kaneda 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (56) References JP 59-226210 (JP, A) JP-A-57-119108 (JP, A) JP-A-54-114613 (JP, A)

Claims (4)

[Claims] 1. Steam is supplied to a turbine through an intercept valve, the opening of the intercept valve is controlled according to the speed of the turbine, and when the turbine speed may become excessive, An intercept valve abrupt closing control device for abruptly closing an intercept valve, which responds to the aforesaid intercept valve closing circuit that generates a judgment output when there is a risk that the turbine speed becomes excessively high. And a means for rapidly closing the intercept valve, and a quick closing operation prohibiting means for prohibiting the operation of the intercept valve abrupt closing means after the intercept valve is once abruptly closed until the intercept valve is fully opened. An intercept valve rapid closing control device characterized in that 2. The determination that the turbine speed may be excessively high is made based on whether or not the deviation of the actual intercept valve opening degree from the intercept valve opening instruction exceeds a predetermined value. The intercept valve rapid closing control device according to claim 1. 3. The intercept valve rapid closing control device according to claim 1, wherein the determination that the turbine speed may be excessively high is performed based on the turbine speed. 4. The method according to claim 1, wherein the means for inhibiting the operation of the intercept valve abrupt closing means prevents the judgment output from being supplied to the intercept valve abrupt closing means. The intercept valve sudden closing control device according to the item.