JPH03149303A - Steam turbine control device - Google Patents

Abstract

PURPOSE:To prevent fluctuation of turbine inlet steam pressure by changing a real opening degree of a turbine bypass valve when it is operated in closure at the same speed as that of the real opening degree of a steam regulating valve in a reverse direction. CONSTITUTION:A turbine speed and turbine inlet steam pressure are controlled by controlling respective opening degrees of a steam regulating valve 3 for regulating a flow quantity of steam flowing in a turbine 4, and a turbine bypass valve 6 for regulating the flowing quantity of steam bypassing the turbine 4. A changing rate limiter 23 is provided for operating so that the real opening degree of the turbine bypass valve 6 is changed at the same speed as that of the real opening degree of the steam regulating valve 3 in a reverse direction, when the turbine speed is slow and the opening degree of the steam regulating valve 3 is increased. It is, thus possible to prevent turbine inlet steam pressure from increasing rapidly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a steam turbine control device in a power plant. (Prior Art) FIG. 4 shows an example of a turbine steam system in a nuclear power plant. In FIG. 4, steam generated in the reactor 1 passes through the main steam stop valve 2 and the steam control valve (hereinafter referred to as C) 3, flows into the turbine 4, drives the turbine, and is transferred to the condenser 5. The water is condensed.

Further, a part of the steam passes through a turbine bypass valve (hereinafter referred to as TBV) 6 from before the main steam stop valve 2, bypasses the turbine 4, and is dropped into the condenser 5.

Normally, the main steam stop valve 2 is kept fully open, and the valve openings of CV3 and TB6 are adjusted to control the turbine inlet steam pressure and turbine speed. In this case, the actual pressure and actual speed are detected by a pressure detector 7 provided in front of the main steam stop valve and a speed detector 8 attached to the turbine shaft, respectively.

FIG. 5 shows a control system of a conventional steam turbine control device. In FIG. 5, the set speed V□ set by the speed setter 9 and the actual speed v2 detected by the speed detector 8 are subtracted by an adder 10, and the speed deviation v3 (=Vx V2) is the speed control command. Output as a value. On the other hand, the pressure setting device 11
The set pressure v4 and the actual pressure v5 detected by the pressure detector 7 are subtracted by the adder 12, and the pressure deviation v6 (=v
s V4) is taken out via the phase corrector 13 as a pressure control command value \17. The speed control command value v3 and the pressure control command value v2 are input to the low value selector 14, and the lower command value is selected and output as the CV opening command value v8, which is detected by the valve position converter 15. It is compared with the actual opening degree signal v9 of CV3 by the adder 16, and the deviation signal V(=Vll-V9) is sent via the valve driver 17 to the valve opening degree of CV3 corresponding to the opening command value VB. control.

On the other hand, the pressure control command value v7 and the CV opening command value v8
is subtracted by the adder 18, and the difference VfuV8 is TBV6
is output as the opening command value V□, and the valve position converter 19
The adder 20 compares the actual speed signal of TBV6 detected at -15,y□2 with the deviation V 5 (=V engineering), v
1, 2) controls the valve opening of the TBV 6 via the valve driver 21 in accordance with the opening command value V□1.

Using the above control system, the following pressure control operation is normally performed. In pressure control operation, the above V.

The set speed V1 is set high so that V is a little higher than v7, and the pressure control command value V is selected as a low value to become the CV opening command value vl]. Therefore, ■,, = vI
, so V and □ become zero, TBV6 becomes fully open, and pressure control is performed only with CV3.

During pressure control operation, if the actual speed V2 becomes -1 twice, V decreases and v3 becomes lower than V7, so c■Opening command value v6
becomes ~I3, and the CV opening degree is controlled in the closing direction. At this time, V7>V, Donarunote, V1. ＞Otonari, TBV
6 is controlled in the opening direction. In other words, the amount of steam flowing into the turbine 4 decreases by closing CV3, and the excess steam flows into TB.
Steam flows to V6, and the steam flow rate seen from the reactor 1 becomes constant,
The input steam pressure of the turbine 4 also becomes constant.

(Problem to be solved by the inventor) = 3- As mentioned above, during normal pressure control operation, even if the actual speed and actual pressure fluctuate, the opening degrees of CV3 and TBV6 do not lag behind their respective specified values. There is no problem because it follows, but
When a sudden disturbance occurs due to a system accident, the following problems occur.

That is, as shown in the time chart of Fig. 6, if the actual speed v2 suddenly increases from the reference speed at time 1 during pressure control operation, then the time when V3 decreases to V, <v7 is set to 2.
, V5 decreases and the opening degree V9 of CV3 also decreases, and at the same time, the opening command value Vll of TBV6 increases, and T B
The actual opening degree V12 of V6 also increases with V□. In this case, the closing operation amount ~18 of CV3 and the opening operation amount V+2 of T 13 V 6 are equal in magnitude, so no fluctuation occurs in the actual steam pressure of the turbine. When the speed suddenly returns to the reference speed, ■8 changes to the opening direction and v4□ changes to the closing direction. In this case, the speed of change and opening/closing amount of opening command value v6 and V□1 are the same, but the actual opening speed of CV3 (V, ) and closing speed of TBV6 (
V□2) is different because T B V 6 closes faster.

When the steam from the reactor 1 is limited to 1, the steam pressure V increases. Therefore, the pressure control command value V1 is in the opening direction, and the TBV6 begins to open from time 1 and fully opens at time 11, but at this point, the artificial vapor pressure v5 exceeds the limit value, and the reactor protection interlock is activated. could activate and lead to a reactor scram.

As a countermeasure for this, there is a method to make the opening speed of CV3 quickly follow the CV opening command value ■8, but since the time difference between opening time 4 and t5 is short, less than a few seconds, increasing the opening speed of CV3 is a way to It is difficult to increase the opening speed because of mechanical thermal stress and limitations from the hydraulic system that operates the CV3.

The present invention provides a steam turbine control device that controls the closing speed of a TBV by following the actual opening degree of the CV when a sudden opening command of the CV is input, thereby preventing fluctuations in the turbine inlet steam pressure. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) The present invention controls the opening degree of a steam control valve that adjusts the flow rate of steam flowing into the turbine and a turbine bypass valve that adjusts the flow rate of steam bypassing the turbine, thereby controlling the turbine speed and the turbine speed. In a steam turbine control device that controls inlet steam pressure.

A change rate limiter is installed in the opening command value of the turbine bypass valve, which operates when the turbine bypass valve closes so that the actual opening of the turbine bypass valve changes in the opposite direction at the same speed as the actual opening of the steam control valve. It is something that

(Function) Even when the turbine speed decreases and the opening degree of the steam control valve is increased, the bypass valve opening degree is decreased in proportion to the increase in the opening degree of the steam control valve, thereby preventing the turbine inlet steam pressure from rising rapidly. It can be prevented.

(Example) An example of the present invention is shown in FIG. Figure 1 shows the conventional 5th
The change rate limiter 23 has been added to the figure, and the rest is the same as in FIG. 5.

The operation shown in FIG. 1 is shown in FIG. 3 below. During pressure control operation, when the actual speed v2 starts to increase at time 70, V7 starts at time 2.
>V, and the C■ opening command value v8 changes in the closing direction,
The CV actual opening degree vg also changes in the closing direction following V. At this time V? > vs, so the V mechanism moves in the opening direction. Also, since V□ is in the open direction, the output Vi of the rate of change limiter
s outputs v0□ as it is, and TBV6 operates in the opening direction.

Next, when the actual speed v2 starts to return to the reference value at t, the CV opening command value V becomes in the opening direction, and at 6, when the actual speed v2 returns to the reference value, the CV opening command value V8 also returns to the original value. However, the actual CV opening degree V continues to rise slowly, lagging behind vll. In addition, the TBV opening command value V □ is also the Cv opening command value v8
, and becomes fully closed at time 6. However, since the output VXS of the rate of change limiter decreases slowly to the same extent as the opening speed of Cv, the TBV actual opening degree Vta also decreases slowly. As a result, the speed of change in the opening direction of CV3 and the TBV6
Since the rate of change in the opening direction of the reactor 1 remains the same, the total flow rate from the reactor 1 does not change, and therefore the turbine inlet steam pressure does not fluctuate.

Another embodiment of the invention is shown in FIG. In FIG. 2, a signal fu circuit 31 is provided which bypasses the rate of change limiter in FIG. 1. As a result, the exclusion condition is satisfied during pressure control only with TBV6, and the TBV opening command value V□ is input to the adder 20 without going through the rate of change limiter, so the controllability of TBV6 is controlled without impairing the controllability. can be carried out.

〔Effect of the invention〕

As explained above, according to the present invention, even if the CV opening command value suddenly changes in the opening direction, the TBV opening is controlled in the closing direction at a speed comparable to the opening direction speed of the CV actual opening. and the amount of change is also the same, so the total flow rate of steam flowing to the CV and TBV does not change, and therefore, no fluctuation occurs in the turbine inlet steam pressure.

Further, the present invention can be easily realized by simply adding a rate of change limiter to a conventional control device.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram showing one embodiment of the present invention, FIG. 2 is a control system diagram showing another embodiment of the invention, and FIG. 3 is a time chart showing the operation of the embodiment of FIG. 1. Fig. 4 is a system diagram showing a general configuration of a turbine steam system, Fig. 5 is a control system diagram showing an example of a conventional steam turbine control device, and Fig. 6 is a system diagram showing a general configuration of a turbine steam system.
The figure is a time chart showing the operation of the apparatus shown in FIG. ■・−・Reactor 2...Main steam stop valve 3...Steam control valve 4...Turbine 5...Condenser 6...Turbine bypass valve 7...Turbine inlet pressure detector 8...Speed detector 9...Speed setter 10.12, 16, 18, 20...Adder 17, 21
...-Valve position driver 11...Pressure setting device 13...Phase compensator 14...Low value selector 15, 19...Valve position converter 23...Rate of change limiter 31...・Rate of change limiter exclusion circuit ``--1'.,-. 苓;--: Sub*door: 蓓: ■ World

Claims (2)

[Claims] (1) Means for comparing the pressure control signal and speed control signal of the power plant and selecting the lower value; means for controlling the steam control valve opening by using the selected signal as a steam control valve opening command signal; In a steam turbine control device having means for subtracting a steam control valve opening command signal from a control signal and controlling the turbine bypass valve opening as a turbine bypass valve opening command signal, the turbine bypass valve opening command signal includes:
A steam turbine control device comprising a rate-of-change limiter that operates only when the turbine bypass valve is in the closing direction so that the closing speed of the turbine bypass valve does not exceed the maximum opening speed of the steam control valve. (2) The steam turbine control device according to claim 1, further comprising an exclusion circuit that excludes the rate of change limiter when the pressure is controlled by a turbine bypass valve.