JPS62261606A - Controller of steam turbine - Google Patents

Abstract

PURPOSE:To enable quick speed settling of a turbine by mounting a control means which selectively opens appropriate ones of a plurality of interception valves (IVs) after load of a steam turbine is cut off, to restrain secondary peak of the steam turbine. CONSTITUTION:A power load unbalance circuit 30 is integrated in the control circuits of some of a plurality of IVs which are opened again to settle the revolution speed of a steam turbine after load thereof is cut off. When load of the steam turbine is cut off, the power load unbalance circuit 30 is activated to close a switch 32 and a bias signal 31 is added to an IV opening command signal 16 so that the IVs would not be opened. Among a plurality of IVs, some to which bias signal is not added will then be opened to reduce steam flow rate of IVs with respect to revolution speed signals. The energy for reaccelerating the steam turbine can then be also reduced so that stable speed control can be performed.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Application Field) The present invention relates to a steam turbine control device, and is particularly useful for controlling the speed of a large-capacity steam turbine for thermal or nuclear power generation. The present invention relates to a steam turbine control device suitable for later obtaining rapid settling characteristics.

(Prior art) A large-capacity reheat cycle steam turbine has a steam control valve (hereinafter referred to as C) that controls the flow rate of main steam flowing from the boiler to the high-pressure turbine, and a steam control valve (hereinafter referred to as C) that controls the flow rate of main steam flowing from the boiler to the high-pressure turbine, and An intercept valve (hereinafter referred to as IV) is provided to control the flow rate of reheated steam flowing through the vessel and into the intermediate pressure turbine.

Normally, during operation of the turbine, IV is fully opened, and the amount of steam passing through the steam turbine is controlled by C⊛ to control the rotational speed or load of the turbine.

FIG. 5 shows a system configuration diagram of such a well-known reheat cycle steam turbine. As shown in the figure, the water supplied from the water pump is heated in boiler 1 and turned into steam, which then flows into the CV
2 to the high pressure turbine 3. The exhaust steam from the high-pressure turbine 3 is again introduced into the reheater 1a of the boiler 1 to be converted into reheated steam, and is introduced in parallel to the intermediate-pressure turbine 5 through the parallel IVs 4a and 4b. The steam from the intermediate pressure turbine 5 further undergoes work in the low pressure turbine 6 and is sent to the condenser. The high-pressure turbine 3, intermediate-pressure turbine 5, and low-pressure turbine 6 driven in this manner drive the power generation ta7 to generate power.

In such a configuration, CV2 and IV4a of the steam turbine
, 4b (hereinafter, these IVs are collectively referred to as IV4) and other control valves are generally known as mechanical-hydraulic type and electro-hydraulic type.

FIGS. 6 and 7 are block diagrams of conventional electrohydraulic steam turbine i and II control devices.

Now, in the configuration shown in FIG. 6, the rotational speed of the steam turbine is detected by a speed detecting section 9 such as a speed pickup, and the detected signal is compared with the speed setting signal from the speed setting section 10, and the deviation signal 11 is It is sent to the CV adjustment rate setting section 12 and the IV adjustment rate setting section 13. The signal from the load setting section 14 is added to the output of the CVa constant rate setting section 12, and the C
A V opening command signal 15 is sent out. On the other hand, a signal obtained by multiplying the signal from the load setting section 14 by (CVli constant rate/IVI constant rate) is added to the output of the IVm constant rate setting section 13 to obtain the opening command signal 16. In addition, during normal operation, the IV
4, an IV full open bias 17 is added to the IV opening command signal 16.

FIG. 7 shows the valve opening degree control device of IV4. As shown in the figure, the IV opening command signal 16 passes through the IVM degrees 1! The position III of the IV oil cylinder 22 is controlled via. On the other hand, if the output from the preamplifier 19 becomes a negative signal below a certain value, that is, I
When the VrlB degree command suddenly decreases, this is detected via the closing direction deviation detection section 25, and the rapid action solenoid valve 26 is energized and the IV oil cylinder 22 is rapidly closed. In addition, IV oil cylinder 2
The valve opening degree of No. 2 is detected by a valve opening degree detector 23, demodulated by a demodulator 24, and negatively fed back to the input side of the preamplifier 19.

Generally, 2111 or more IV4s are installed in a reheat steam turbine, and each IV4 is installed with an IV valve opening degree control I device having a configuration similar to that shown in FIG. 7.

Now, taking as an example when the steam turbine is operating at rated load, the Cv open lη command signal 15 and the IV level command signal 16 output 100% signals from the load setting unit 14, which are not shown in the figure. The C■ oil cylinder is at the rated position, and the IV oil cylinder 22 is fully open. When load shedding is performed on the steam turbine generator i from this state, the signal of the load setting unit 14 immediately becomes zero, CV2 and IV4 are suddenly opened to cut off the steam flowing into the steam turbine, and the steam turbine rotates. Control the rise.

At this time, the steam in the boiler reheating section is confined by IV4, but after the steam turbine reaches its maximum rotational speed, when the rotational speed begins to drop to approximately 102%, IV4 begins to open and the boiler is reheated. Speed control is performed while releasing steam from the hot section.

Thereafter, when almost all of the steam trapped in the boiler reheating section has been released, CV4 begins to slow down, and the steam turbine settles in a state where the no-load steam flow is flowing.

(Problem to be solved by the invention) Generally, the steam flowing into the intermediate pressure turbine 5 has a large specific volume, so a large diameter valve is required for the IV4, and multiple valves are often used. . Therefore, when IV4 is heard as the rotational speed decreases after the load interruption, enough steam will flow in to re-accelerate the steam turbine even with a small opening.

For this reason, a so-called secondary peak phenomenon occurs as shown in section P of the operating characteristic diagram in FIG. 8 (A>).

In recent years, steam turbine control equipment uses sampling 1Ill.
Digital control devices that perform fil have been put into practical use. However, sampling control tends to generate the IV opening command signal 16 with a slight delay with respect to the rotational speed of the turbine. In other words, when the turbine rotational speed decreases after the load is cut off, IV4 does not open even if the turbine rotational speed decreases to the turbine rotational speed preset by the IV regulation rate setting unit 13, and IV4 opens with a delay of the sampling period. During this time, the turbine rotation speed continues to drop, so
A larger IV opening command signal 16 will be applied to the IV opening control device. As a result, the opening degree of IV4 becomes larger, and excessive steam flows into the intermediate pressure turbine 2. For this reason, 81 in the operating characteristic diagram of Fig. 8(B)
As shown in section 2, this results in further aggravation of the secondary peak phenomenon.

However, at this time, an increase in rotational speed was detected and the I
Although the control system acts to close V4, the IV closing direction signal at this time may cause the closing direction deviation detection section 25 to operate, causing the rapid action solenoid valve 26 to operate. In this case, as shown in the operating characteristic diagram of FIG. 8(C), IV4 is suddenly closed.

Once this phenomenon occurs, the speed control system of the steam turbine will perform discontinuous control, repeating IV slight opening, speed increase, IV sudden closing, and speed drop. This phenomenon is repeated until the reheating steam pressure has almost completely escaped, and may reach about 50 times in most cases.

In this way, if the IV quick closing operation is repeated unnecessarily,
This prolongs the settling time of the steam turbine after the load is cut off, and the rotating parts of the steam turbine are maintained at a high speed. This results in a significant reduction in the life of the steam turbine. Also, I
By repeating rapid movements unnecessarily, V4 itself
This results in accelerated wear of sliding parts, etc. In particular, this phenomenon becomes more pronounced in two-stage reheat turbines and nuclear power turbines that have a large number of IV4 valves.

Therefore, the object of the present invention is to solve the problems of the prior art as described above, that is, to suppress the secondary peak of the steam turbine due to the repeated opening and closing phenomenon of the IV that occurs after the load is cut off, and to provide a steam turbine that enables rapid turbine settling. controllll
The goal is to provide equipment.

[Structure of the invention]

(Means for Solving the Problems) The steam turbine control device of the present invention leads main steam from a boiler to a high-pressure turbine, and passes exhaust steam from the high-pressure turbine through a reheater to generate regenerated steam. In a steam turbine control device for controlling a reheat cycle steam turbine that guides hot steam in parallel to an intermediate pressure turbine via each intercept valve, a first detection means for detecting a load cutoff of the reheat cycle steam turbine; a second detection means for detecting the rotation speed of the reheat cycle steam turbine; a third detection means for detecting the pressure of the reheat steam; and a third detection means for detecting the pressure of the reheat steam turbine;
, control means for selectively closing the plurality of intercept valves after load cutoff of the reheat cycle steam turbine according to detection signals obtained by the second and third detection means. That is.

(Function) According to the above configuration, the number of open<IVs is limited by the rotational speed control signal when the IV restarts after the load cutoff of the steam turbine,
IV when the IV begins to open due to turbine speed reduction
The increase in the flow rate of reheated steam flowing into the intermediate-pressure turbine is made slow with respect to the increase in the valve opening of the intermediate-pressure turbine, thereby preventing the natural-air turbine from being accelerated unnecessarily.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partial block diagram of a steam turbine control device according to an embodiment of the present invention. As shown in the figure, a power load unbalance circuit 30 generates a signal based on the deviation between the output signal of the power generation line driven by the steam turbine and the reheat steam pressure signal, and closes the switch 32.

When the switch 32 closes, the bias signal from the bias setting device 31 is applied to the IV opening degree control function section 18 corresponding to a specific IV among the plurality of IVs 4, for example, the front stage of the IV opening control function section 18a.

In this configuration, when the steam turbine is load cut off, the power load unbalance circuit 3o is activated, the switch 32 is closed, and a bias signal is added to the IV opening command signal 16 from the bias setting device 31. At this time, the relationship between the IV opening command signal 16 and the output of the IV opening i and II control function section 18 shifts from the solid line characteristic Q1 to the broken line characteristic Q2, as shown in the characteristic diagram of FIG. That is, with the small IV opening command signal 16 after the load is cut off, the IV will not open, and only the IV4 to which the bias signal is not applied will operate as usual based on the rotational speed signal.

As a result, after load shedding, some ■
Since only v will open, I for the same rotation speed signal
The steam flow in V is reduced and the energy to re-accelerate the steam turbine is reduced, resulting in stable speed control. That is, as shown in the operating characteristic diagram of FIG. 3, even if the rotational speed of the steam turbine decreases, the IV does not open suddenly, so the steam turbine stably settles without having a secondary peak.

When IV4 opens and all the reheated steam is released, the power load imbalance circuit 30 is reset. As a result, the bias signal applied to the control system of the specific IV4 is turned off, so that the IV4 returns to its normal control state.

FIG. 4 shows a partial block diagram of a steam turbine control device according to another embodiment of the present invention.

The difference between the configuration shown in FIG. 1 and the configuration shown in FIG. This suppresses the secondary peak caused by the same operation of IV4 during turbine deceleration.

In addition, in each of the above embodiments, a specific IV among a plurality of IVs
Although the case where the same operation is suppressed is illustrated, the implementation of the present invention is not limited to this, but the opening suppression means υ1 may be added to all valves and this may be operated selectively. Good too.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to quickly settle the steam turbine after the steam turbine load is cut off, and to minimize the operation in the high rotation range that affects the life of the steam turbine. It is possible to provide a steam turbine control device that can achieve desired control characteristics without affecting normal operation at all.

[Brief explanation of drawings]

Fig. 1 is a partial block diagram of a steam turbine υ control device according to an embodiment of the present invention, Fig. 2 is an IV opening 1 command signal diagram, and Fig. 3 is a diagram of the IV opening 1 command signal when the present invention is implemented. An operating characteristic diagram showing the turbine rotational speed and the movement of IV, FIG. 4 is a steam turbine 1IIJ'a according to another embodiment of the present invention.
A partial block diagram of the device, FIG. 5 is a system configuration diagram of a well-known reheat cycle steam turbine, FIGS. 6 and 7 are block diagrams of a conventional steam turbine control device, and FIG. 8 is a diagram of a conventional steam turbine control device. FIG. 3 is an operating characteristic diagram showing the rotational speed of the steam turbine and the movement of IV. DESCRIPTION OF SYMBOLS 1... Boiler, 2... Steam control valve, 3... High pressure turbine, 4... Intercept valve (IV), 5...
Intermediate pressure turbine, 7... Generator, 16... I ■Opening command signal, 18-IV Opening $lIIlf31am
, 30.l<'7-0-unbalance circuit, 31...bias setting device, 32...switch. Applicant's agent tli Fuji - Male ≧ Four tumors F Hime Kaeyo R District 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. Main steam from the boiler is guided to a high-pressure turbine via a steam control valve, and exhaust steam from the high-pressure turbine is passed through a reheater to obtain reheated steam, which is intercepted. A steam turbine control device for controlling a reheat cycle steam turbine that is guided in parallel to an intermediate pressure turbine via a valve, comprising: a first detection means for detecting load cutoff of the reheat cycle steam turbine; a second detection means for detecting the rotation speed of the reheated steam; a third detection means for detecting the pressure of the reheated steam; and a third detection means for detecting the pressure of the reheated steam. A steam turbine control device comprising: control means for selectively opening the plurality of intercept valves after a load cutoff of a reheat cycle steam turbine. 2. The steam turbine control device according to claim 1, wherein the control means includes bias means for applying a bias to the control system of a specific intercept valve.