JPH0751886B2 - Control method for steam turbine - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an electric / hydraulic steam turbine control system using a digital control system.

[Technical background of the invention and its problems]

In a steam turbine plant such as a thermal power plant or a nuclear power plant, heat energy generated in a boiler or a nuclear reactor is guided to a steam turbine through steam, and a generator connected to this is rotated to output electric energy. There is.

FIG. 4 shows, as an example of a steam turbine plant, a main part of a steam system in a nuclear power plant including one high-pressure turbine and three low-pressure turbines.

In the figure, the steam generated in the reactor 1 enters the high pressure turbine 4 through the main steam stop valve 2 and the steam control valve 3,
After working here, it is dehumidified in the moisture separator 5, splits in the three steam pipes equipped with the intermediate steam stop valve 6 and the intercept valve 7, enters the three low pressure turbines 8 and rotates the steam energy. After being converted into energy, it is introduced into the condenser 9 and becomes condensed water.

Rotational energy of the high-pressure turbine 4 and each low-pressure turbine 8 is transmitted to the generator 10, converted into electric energy and output to the electric power system.

Between the reactor 1 and the condenser 9, a bypass line is normally provided, which bypasses the high-pressure turbine 4 and the low-pressure turbine 8 and directly connects the upstream side of the main steam stop valve 2 and the condenser 9. Has been. This bypass line is installed in the reactor 1 so that the rotation speed of each steam turbine does not rise when the load of the generator 10 is cut off.
It is provided in order to directly drop the steam generated in the condenser 9 to the condenser 9, and a bypass valve 11 is inserted in the middle thereof.

In the steam turbine system configured as described above, as a control device for the steam control valve 3, the intercept valve 7, and the bypass valve 11, a mechanical control system has been widely used in the past. In addition to capacity and automation, in order to respond to cooperation with other plants linked to the same electric power system, etc.
There is a tendency to shift to a hydraulic control system, and recently,
In order to meet the needs for improved reliability against noise, response to complicated functions, and ease of adjustment / maintenance, electrical / hydraulic control methods mainly for analog arithmetic circuits to electrical circuits mainly for digital arithmetic circuits・ Transition to hydraulic control system is expanding.

FIG. 5 shows a configuration example of a valve position control system of the steam control valve 3. The hydraulic cylinder 12 that drives the steam control valve 3 includes a steam control valve rapid actuation solenoid valve 3a, a steam control valve servo valve 3b, and a steam control valve. The high pressure control oil line H and the drain oil line D are connected via the regulator valve shutoff valve 3c, and the piston rod that moves up and down in the hydraulic cylinder 12 detects the opening degree of the steam regulator valve 3. The device 3d is connected.

The structure of the valve position control system of the intercept valve 7 is the same as that of the steam control valve 3 described above. That is, as shown in parentheses in Fig. 5, the steam control valve rapid actuation solenoid valve 3a is used as the intercept valve quick actuation solenoid valve 7a, the steam control valve servo valve 3b is used as the intercept valve servo valve 7b, and the steam control valve shutoff valve is used. 3c to intercept valve shutoff valve 7c, and steam regulator valve 3 opening detector
If 3d is changed to the opening detector 7d of the intercept valve 7, a hydraulic cylinder control system of the intercept valve 7 is constructed.

The valve position control system of the bypass valve 11 is, as shown in FIG. 6, a bypass valve quick-acting solenoid valve that controls the amount of oil between the hydraulic cylinder 13 and the high-pressure control oil line H and the drain oil line D.
11a, bypass valve servo valve 11b, and high pressure control oil line H
It consists of an accumulator 14 connected in the middle of the pipe. 11
d indicates an opening detector.

FIG. 7 is a block diagram for explaining the overspeed suppressing function at the time of load interruption of the steam turbine control device of the electric / hydraulic control system configured by the analog arithmetic circuit. The circuit controls the rapid closing of the main steam control valve 3. Power load unbalance circuit 15 The intercept valve abrupt closing circuit 16 that controls the abrupt closing of the intercept valve 7, and the bypass valve 11 abruptly in order to suppress the pressure rise of the main steam caused by the abrupt opening of the main steam control valve 3. The bypass valve rapid opening circuit 17 for opening is provided.

In FIG. 7, at the same time as the load cutoff occurrence 20, the load (generator current) sudden decrease detection circuit 21 operates to establish a logical product 22 with the power load unbalance circuit operation load detection circuit 23, and the power load unbalance signal is output. To raise
The steam control valve rapid actuation solenoid valve 3a is excited, and the steam control valve 3
To close.

The output signal of the power load unbalance circuit 15 is also input to the load setting device 24, and the output of the load setting device is cleared when the logical product of the power load unbalance circuit 15 is established. Although there is a close relationship between the output signal of the load setting device 24 and the opening degrees of the steam control valve 3 and the intercept valve 7, the description thereof is omitted because it is not directly related to the present invention.

On the other hand, at the same time when the load is cut off 20, the rotational speed of the steam turbine rapidly increases 25. This signal is sent from the calculator 26 to the load setter 24
Is added to the output signal clear of the intercept valve to become the intercept valve rapid closing signal, and it is checked whether or not the condition 28 described later is satisfied, and if satisfied, it is connected to the hydraulic cylinder 12 of the intercept valve 7 (Fig. 5). The operated intercept valve servo valve 7b is operated in the closing direction.

The hydraulic cylinder 12 also operates in the closing direction when the servo valve 7b operates in the closing direction, but the actual opening detected by the opening detector 7d cannot be followed because the closing direction signal is abrupt, and the condition 2
8, i.e. | intercept valve opening request signal-actual opening signal |> α α: Establishes a preset deviation value. As a result, the logical product 30 of the condition 28 and the intercept valve rapid closing circuit actuation load detection circuit 29 is established, the intercept valve rapid actuation solenoid valve 7a is excited, and the intercept valve 7 is rapidly closed.

In addition, in the bypass valve 11 as well, the load setting device clear signal 24 causes the opening request signal to the steam control valve 3 to instantly become zero.
The bypass valve opening request signal suddenly increases 31, condition 32, that is, | bypass valve opening request signal-actual opening signal |> β β: a preset deviation value, and the bypass valve rapid opening circuit 17 is established. The bypass valve rapid actuation solenoid valve 11a is excited, and as a result, the bypass valve 11 is rapidly opened.

The concept of the electric / hydraulic control device and the analog electric / hydraulic control device of the digital control system for steam turbine control is basically the same, but the digital control system has a sampling cycle and therefore has a control system. The difference is that the dead time element is included.

For example, if the sampling period is t ₁ msec, the total t ₁
It should be noted that a dead time element of × (2 to 3) m sec is included, and especially in the case of transient changes such as when the load of the steam turbine is cut off, this dead time element has a result that cannot be ignored. Invite.

In the case of the digital control method, the valve closing characteristic of the steam control valve 3 at the time of load cutoff is that the calculation processing function does not intervene in the signal path on the way from the power load unbalance circuit 15 to ON-
Since the signal is transmitted by the OFF signal, the dead time element does not intervene before the closing operation starts, but the delay element intervenes in the intercept valve rapid closing circuit 16 and the bypass valve rapid opening circuit 17, so their closing characteristics There will be a delay in the open direction characteristics.

FIG. 8 shows a generator load 50, a power load unbalanced circuit signal 15, a turbine speed 25, a steam control valve opening 3, an intercept valve opening 7, a main steam pressure 51 when a load cutoff occurs at time T ₁ . The change in the bypass valve opening 11 is shown. In the figure, the solid line shows the case of the analog control system, and the broken line shows the case of the digital control system.

As is clear from this figure, the intercept valve 7 and the bypass valve 11 are affected by the dead time component t1 × (2-3) m
The start of the closing or opening operation is delayed by sec, and as a result, the peak values of the turbine speed 25 and the main steam pressure 51 are higher in the digital control method than in the analog control method.

As one means for solving such a problem, a circuit shown in the control block diagram of FIG. 9 has been devised.

This circuit inputs the output of the power load unbalance circuit 15 to the steam control valve rapid actuation solenoid valve 3a, excites this to rapidly close the steam control valve 3, and outputs the output of the power load unbalance circuit 15 to a logic circuit. Addition to the output of the intercept valve rapid closing circuit 16 or the bypass valve rapid opening circuit 17 in 33, 34, the output of these OR circuits is input to the intercept valve rapid actuation solenoid valve 7a, bypass valve rapid actuation solenoid valve 11a, The intercept valve 7 and the bypass valve 11 are rapidly closed and opened to remove the influence of the dead time factor.

However, the system of FIG. 9 may adversely affect the hydraulic system and the hydraulic cylinder as described below.

Fig. 10 shows the generator load when the control block diagram of Fig. 9 is applied to the digital steam turbine control system.
0, power load unbalance circuit signal 15, turbine speed 25, steam control valve 3, intercept valve 7, valve opening degree of bypass valve 11, exciting signals of quick-acting solenoid valves 3a, 7a, 11a,
The figure shows how the open / close signals to the servo valves 3b, 7b, 11b and the hydraulic pressure of the high pressure control oil line H and the drain oil line D are changed.

In the same figure, if a load cutoff of the generator occurs at time T ₁ , the quick-acting solenoid valves 3a, 7a, 11a of the respective valves receive a signal from the power load unbalance circuit 15 and have a dead time element. Since it is operating without any action, the steam control valve 3,
Intercept valve 7 and the bypass valve 11 is time T _2, and later,
Start quick closing or quick opening respectively.

However, it should be noted here that each servo valve 3b, 7
They are the timing when the opening / closing signal is input to b and 11b and the transitional change of the control hydraulic pressure accompanying it.

For example, in the case of the steam control valve 3, the steam control valve 3 starts to close at time T ₂ due to the operation of the rapid operation solenoid valve 3a of the steam control valve, and is fully closed at time T ₃ , but the steam control valve 3 Servo valve 3b
Signal (this signal is calculated by the deviation signal between the turbine speed setting signal and the actual speed signal, and a closing direction signal is input to the servo valve 3b in response to an increase in turbine speed). Remains an open signal between times T _{2 and} T ₃ .

This is caused by the influence of the dead time element essentially provided in the digital control method, but such a delay in the operation of the servo valve 3b in the closing direction causes the high pressure control oil H shown in FIG. The oil is drained through the steam control valve servo valve 3b and the hydraulic cylinder 12. As a result, H _{3 in} FIG.
As shown in, the hydraulic pressure of the high pressure control oil line transiently drops,
In some cases, the amount of oil required may exceed the hydraulic system capacity of the steam turbine, and the function of the hydraulic system may be lost.

Similarly to the steam control valve 3, the intercept valve 7 has a possibility that the hydraulic pressure H ₇ of the high-pressure control oil line is significantly reduced, and the function of the hydraulic system may not be achieved.

The steam control valve shutoff valve 3c and the intercept valve shutoff valve 7c are installed in order to prevent the high pressure control oil H from being turned into drain oil from the servo valves 3b and 7b through the hydraulic cylinder 12, but the orifice Since the operation is delayed due to 12a (Fig. 5), the interrupting function of the high pressure control oil H cannot be achieved instantaneously.

Next, the change in hydraulic pressure in the bypass valve 11 will be described with reference to FIGS. 6 and 10. At time T ₁ , an excitation signal is input to the bypass valve rapid actuation solenoid valve 11a, and the high pressure control oil H is supplied to this solenoid valve. It goes under the hydraulic cylinder 13 via 11a. Further, the high-pressure control oil line above the hydraulic cylinder 13 is drained through the bypass valve rapid actuation solenoid valve 11a to operate the valve in the opening direction.

However, since the signal to the bypass valve servo valve 11b between times T2 and T3 is a closed signal, the high-pressure control oil H flows into the lower part of the hydraulic cylinder 13 and is simultaneously drained through the bypass valve servo valve 11b. It will delay the opening time of 11.

On the other hand, the oil above the hydraulic cylinder 13 is bypass valve servo valve.
When the opening operation of 11b occurs, the oil is drained together with the bypass valve rapid operation solenoid valve 11a and the servo valve 11b.However, due to the delay of the opening operation of the servo valve 11b, only the bypass valve rapid operation solenoid valve 11a. This will allow the oil to escape.
That is, the delay in the escape of the oil on the upper side of the hydraulic cylinder 13 causes the delay in the rapid opening time.

Generally, an accumulator 14 is installed in the high pressure control oil line of the bypass valve for the purpose of preventing a transient decrease in control oil pressure, and therefore the high pressure control oil line H ₁₁ is connected to the steam control valve 3
Although the oil pressure drop phenomenon like the oil pressure system line of the intercept valve 7 does not occur, on the contrary, since the drain oil of the high pressure control oil is generated, the pressure of the drain oil line D is increased. Normally, the design pressure of the drain oil line does not assume such an abnormal situation, and therefore, there is a possibility of causing equipment damage or oil leakage.

[Object of the Invention]

The present invention has been made to eliminate the above-mentioned drawbacks in the background art, and in a control system of a steam turbine that adopts a digital control system, a steam control valve, a rapid closing of an intercept valve, and a rapid bypass valve when a load is cut off. A steam turbine control system that can be opened in the same way as in the case of an analog control system, and that can safely operate hydraulic systems and equipment without intervening time delay factors in the servo valve's rapid closing and rapid opening signals. The purpose is to provide.

[Outline of Invention]

In order to achieve the above-mentioned object, the steam turbine control system of the present invention, in the electric / hydraulic steam turbine control system by the digital control system, operates by the opening degree request signal to rapidly close the steam control valve and the intercept valve, It is characterized in that a servo valve closing bypass signal is added to a valve position control system for rapidly opening the bypass valve by a power load unbalance circuit that operates under the conditions of steam turbine output and sudden load reduction.

Example of Invention

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

FIG. 1 (a) shows an embodiment in which a power load unbalance circuit 15 is added to the valve position control system of the steam control valve.
The signal 60 from the controlled object is the digital input operation output circuit.
A valve opening request signal 63 is passed through 61 to the valve position control circuit 62.
Is output. This signal 63 is added to a later-described closed bias 71 in an arithmetic unit 64, and the obtained signal 65 is compared with a valve position feedback signal 66 in an arithmetic unit 67 to obtain an amplifier.
After being amplified by 68 and further amplified by the servo valve amplifier 69, the steam control valve servo cylinder 3b is controlled to position the steam control valve hydraulic cylinder 12. The signal from the power load unbalance circuit 15 is input to the relay 70, and the closed bias 71 is transmitted to the calculation decision 64 via the relay contact.
Therefore, the valve opening request signal 65 is lowered to the closed level at the same time as the operation of the power load unbalance circuit 15.

FIG. 2 (a) illustrates the operation of the generator load 50, the power load unbalance circuit signal 15, the valve opening request signal 63, the signal 65, and the relay 70 when a load cutoff occurs at time T ₁ . Here, the broken line shows the case of the conventional method, and the solid line shows the case of the method of the present invention.

FIG. 1 (b) shows an example in which the present invention is applied to a valve position control system of an intercept valve 7 or a bypass valve 11, and the same parts as in FIG. 1 (a) are denoted by the same reference numerals. . In this case, a comparator 72 that operates when the deviation signal between the valve opening request signal 65 and the valve position feedback signal 66 reaches a predetermined level is installed at the output side of the amplifier 68, and the signal from this comparator 72 is Corresponds to the condition 28 of the intercept valve 7 in FIG. 7, that is, | opening request signal-actual opening signal |> α, and the condition 32 of the bypass valve 11, that is | opening request signal-actual opening signal |> β Then, the quick-acting electromagnetic valves of the respective valves are excited to close them rapidly.

In this embodiment, a power load unbalance circuit
At the same time as the operation of 15, the closing signal to the intercept valve servo valve 7b is generated in the same manner as described in FIG. 1 (a), and the comparator 72 also operates without a time delay, so that the intercept in FIG. The quick valve closing circuit 16 and the bypass valve rapid opening circuit 17 are also operated immediately after the load is cut off.Therefore, they are closed or opened rapidly together with the signal from the power load unbalance circuit 15, which shortens the operating time. it can.

FIG. 2B shows the conventional method (chain line) and the first method according to the present invention.
The difference in the control method (solid line) in FIG. 7B is shown. While the operation time of the comparator 72 in the conventional method is T ₂ , (actually, the valve is the power load unbalance circuit 15). The quick actuating solenoid valves 3a, 11a that received a signal from the actuating valve are actuated and are being closed rapidly, so the actuation will start only when the open signal 65 to the servo valve is fully closed. According to the present invention, the servo valve 7b (11
Since the signal to b) reaches the fully-closed level at the same time as the load interruption T _1, the operating point of the comparator 72 also operates without delay and thus plays a sufficient auxiliary role.

FIG. 1 (c) shows an example in which the present invention is applied to the secondary side of the amplifier 68 of the valve position control system. In this case, servo valve 7b (11b)
As the position control signal to the output signal from the amplifier 68 is added with the closing bias signal 71 in the adder 64, it becomes a closing signal at the same time as the operation of the power load unbalance circuit 15, and the servo valves 7b and 11b are closed. Then, the hydraulic cylinder 12 of the intercept valve 7 and the hydraulic cylinder 13 of the bypass valve 11 are operated in the closing direction.

FIG. 3 shows the behavior of the turbine speed, the valve opening rapid actuation solenoid valve excitation signal of each valve, the opening / closing signal to the servo valve, and the hydraulic pressure change of each part when the present invention is applied to the valve position control system.
Although it is shown in comparison with FIG. 10, it can be understood that the closed states of the servo valves 3b, 7b, 11b are secured almost at the same time as the load cutoff occurrence time T ₁ for the reason described above.

At the same time when the power load unbalance circuit 15 is turned on, the steam control valve 3 and the intercept valve 7 are the quick-acting solenoid valves 3a, 7 respectively.
The bypass valve 11 is fully closed by a, and the bypass valve 11 is fully closed by the bypass valve rapid operation solenoid valve 11a and the servo valve 11b.

Servo valve 3b up to time T _2, in the conventional method, the opening request signal to 7b are in an open state, also it to the servo valve 11b is according to the present invention whereas was closed, previously these The signal level of is the closed or open level which is the final purpose.

Therefore, after the quick-acting solenoid valves 3a, 7a, 11a are actuated, at the time when the valves move toward the closing or opening direction, the control oil for the steam control valve 3 and the intercept valve 7 passes through the cutoff valve, the servo valve, and the hydraulic cylinder. There will be no oil path through which the oil is drained.

Therefore, the control oils H ₃ , H ₇ , and H ₁₁ did not fall sharply, and the bypass valve drain oil D did not rise sharply.
There is no fear of causing the drain line D to have a high pressure.

〔The invention's effect〕

As described above, the present invention eliminates the basic dead time element of the digital control system by adding the servo valve closing bias system that operates with the power load unbalance signal to the conventional valve position control system, thus eliminating the load interruption. At the same time steam control valve,
Not only it is possible to close or open each servo valve of intercept valve and bypass valve, but also to prevent transient drop of control oil and transient high pressure of drain line caused by delay of servo valve. Therefore, it is possible to provide a highly reliable steam turbine control system.

[Brief description of drawings]

FIG. 1 illustrates a valve position control system to which the present invention is applied. FIG. 1 (a) is an application example to a steam control valve, and FIG. 1 (b) is an application example to an intercept valve or a bypass valve. FIG. 3 (c) is a graph showing a modified example of FIG. 2 (b), FIGS. 2 (a) and 2 (b) are graphs showing the operation of the method of the present invention in comparison with a conventional example, and FIG. Is an operation explanatory view of the present invention,
FIG. 4 is a system diagram illustrating a main part of a steam system of a steam turbine plant to which the present invention is applied, FIG. 5 is a control system diagram of a steam control valve and an intercept valve, and FIG. 6 is a control system diagram of a bypass valve. , FIG. 7 is a block diagram of a steam turbine overspeed suppressing function in a conventional analog control system, FIG. 8 is a graph explaining a dead time element at the time of load cutoff by a digital control system, and FIG. 9 is a load cutoff by a digital control system. FIG. 10 is a block diagram of a steam turbine overspeed suppressing function at the time of operation, and FIG. 10 is an operation explanatory view of each control element at the time of load interruption by the conventional digital control method. 1 ... Reactor, 2 ... Main steam stop valve, 3 ... Steam control valve, 3a ... Steam control valve rapid-acting solenoid valve, 3b ... Steam control valve servo valve, 3c ... Steam control valve shutoff valve, 3d, 7d, 11d ...
… Openness detector, 4 …… High pressure turbine, 5 …… Moisture separator, 6 …… Intermediate steam stop valve, 7 …… Intercept valve,
7a …… Intercept valve Rapid actuation solenoid valve, 7b …… Intercept valve Servo valve, 7c …… Intercept valve shutoff valve, 8 …… Low pressure turbine, 9 …… Condenser, 10 …… Generator, 11 …… Bypass valve , 11a …… By-pass valve quick-acting solenoid valve, 11b …… By-pass valve servo valve, 12,13 …… Hydraulic cylinder, 15 …… Power load unbalance circuit, 16 ……
Intercept valve rapid closing circuit, 17 ... Bypass valve rapid opening circuit, 71 ... Open bias, H ... High pressure control oil line, D ...
… Drain oil line.

Claims (2)

[Claims] 1. An electric / hydraulic steam turbine control system based on a digital control system, comprising a valve position control system which operates in response to an opening request signal to rapidly close a steam control valve and an intercept valve and to rapidly open a bypass valve, A control method for a steam turbine, characterized in that a servo valve closing bias signal is added by a power load unbalance circuit that operates under the conditions of steam turbine output and sudden load reduction. 2. A valve position control system comprises an amplifier operated by an opening request signal, a servo valve, a hydraulic cylinder, and a valve opening detector, and a power load unbalance circuit signal and a servo valve closing bias signal are sent to the valve. The control system for a steam turbine according to claim 1, wherein the addition is made to the output side of the amplifier of the position control system.