JPS5812444B2 - Steam turbine pressure change control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure change control device for a steam turbine, and more particularly, to a pressure change control device for a steam turbine that is capable of changing a pressure setting value before a regulating valve so as to stably follow the load of the steam turbine. Regarding equipment.

BACKGROUND ART Conventionally, thermal power plants have adopted a constant-pressure operation system in which steam pressure is maintained at constant conditions.

However, in recent years, nuclear power plants have been assigned to handle the base load range, and thermal power plants have been assigned to handle the middle load range.

In this type of operation, the variable pressure operation method, which changes the steam pressure according to the load level, has come to be particularly highly evaluated for the following points.

(a) Since the adjustment valve opening can be operated near fully open, there is less throttling loss.

(Note) Because the main steam temperature is almost constant, there are fewer problems with thermal stress due to load fluctuations.

(c) Since the volumetric flow rate is almost constant, the efficiency of the turbine is high.

(d) The heat retained in the boiler can be effectively used during sudden load changes, resulting in high load followability.

(E) The power saving of the turbine for driving the water supply pump is large.

An example of a steam turbine pressure change control device having the above-mentioned characteristics is shown in FIG.

In FIG. 1, a steam turbine 1 is directly connected to a generator 2, a condenser 3 condenses steam from the steam turbine 1, and a feed water pump 4 sends the condensed water to a boiler 5.

The fuel valve 6 is for regulating fuel to the boiler 5, the regulating valve 7 is for regulating steam pressure to the steam turbine 1, the load detector 8 is for detecting the load condition of the generator 2, and the regulating valve front pressure detector 9 is for regulating the regulating valve. This is for detecting vapor pressure before entering 7.

The function generator 10 outputs a setting signal for adjusting the regulator valve 7 according to the output from the load detector 8, and controls the regulator valve operator 1.
1 is the output pR of the function generator 10 and the pressure detector 9 in front of the regulating valve.
The control valve 7 is operated according to the difference between the output PCV and the output PCV.

The operation of the steam turbine pressure change control device in the above configuration will be explained based on FIG. 1. The steam turbine 1 load Ls
In response to T, the function generator 10 changes the set value PR of the prepressure PCV of the regulator valve 7 of the steam turbine 1, and the regulator valve operator 11 changes the valve opening depending on the deviation from the regulator valve prepressure PCV. Adjust.

The steam circulation system is well known to those skilled in the art, so a description thereof will be omitted.

In the operation according to the method described above, a particular problem is how to change the pre-regulator pressure setting value PR. Conventionally, as shown in FIG. 2A, the steam turbine 1 The pre-regulator pressure setting value PR was changed in accordance with the load Lst.

Figure 2 A is designed to keep the pre-valve pressure set value PR as constant as possible, and when the load increases, the load is 0-LU.
1, LU1-LU2, LU2-Lu3, LU3-Lma
When in the range of x, PR is PL, PM1, PM2, respectively.
, PH.

Similarly, when the load decreases, PHt when LmaX-Ll3
When Lls Ll2, PM2) When Ll2 Llt, PMt y Lls When below, it is PL.

In addition, in the same figure a, ALL is the lower limit value of the adjustment valve opening, and A
LU is an upper limit value, and by making it variable within this range in which the throttle error of the adjusting valve does not become excessive, the sticking phenomenon of the valve is prevented.

The method of changing the pressure set value PR stepwise as shown in this figure has the following problems.

Based on FIGS. 2B and 2C, the response of the load Lst of the steam turbine 1 and the control valve opening ACV to the load request LD will be explained.

t in FIG. 2B.

When the load request LD starts to increase from LUo at the point in time,
Accordingly, the amount of fuel input to boiler 5 is also increased,
Due to the response delay in the amount of steam generated by the boiler 5, the load LsT of the steam turbine 1 also starts up from time t1 with a delay.

At this point, LST=LUO, and the pre-regulator pressure setting value PR is fixed at 9 as shown in FIG.
Since V increases, the adjusting valve opening ACV operates in the opening direction in order to increase the pressure and keep it constant at PL.

Therefore, the load LST of the steam turbine 1 is also equal to the adjustment valve opening A.

■It will rise due to fear. Adjustable valve opening AC as shown in Figure 2 C
At time t2 when V reaches the opening upper limit value AUL, the pressure setting value PR in front of the regulating valve is changed from PL to PM1, and the regulating valve opening ACV suddenly operates in the closing direction, as shown in Fig. 2C. As in, it descends to Aml.

Therefore, the load LsT of the steam turbine 1 also decreases as shown in FIG. 2B.

When the adjustment valve opening degree ACV reaches Am1, the steam energy generated by the boiler and the steam turbine load energy are in a balanced state.

Thereafter, as shown in FIG. 2A, the operation is performed at a constant pressure of PMt, and as the amount of steam generated by the boiler increases, the pressure PCV before the control valve 7 increases.
increases, so the adjustment valve opening degree A.

V operates in the opening direction, and the load LsT of the steam turbine 1 also increases.

Next, at time t3, the pre-regulator pressure setting value PR is changed from PMI to PM2, and the response to the regulator valve opening AcV and the load Lst of the steam turbine 1 is the same as from t2 to t3.

At time t5, load tracking is completed, but the pressure setting value PR before the adjustment valve is at PM2, and the adjustment valve opening ACV is at C in Figure 2.
As shown in the figure, the opening degree is set to Am2, which is lower than the upper limit value AUL.

As is clear from the explanation of FIG. 2, when the load reaches LUI, LU2 2 LU3 in the load increasing process, the adjustment valve opening degree ACV is narrowed down.

This in turn causes a transient load reduction.

Although a detailed explanation is omitted, the operation is similarly carried out along the solid line in FIG. 2A even when the load is reduced, and the load LU3
s At Lgl, a transient load increase is caused in order to open the adjusting valve opening ACV.

In this way, in the conventional method, when the load increases, the control valve opening AC
Since the control valve throttles V and opens the adjustment valve opening Acv when the load decreases, stable load operation cannot be achieved.

The occurrence of such load fluctuations can be easily explained as follows.

In other words, the pressure in front of the control valve pcv with respect to the control valve opening degree ACV
(Load Lst is determined according to PCV.

) is expressed as a first-order lag with a time constant of several minutes, whereas the response of the turbine load Lst exhibits substantially differential characteristics.

Therefore, when the adjustment valve opening degree ACV is reduced for the purpose of increasing the load, immediately after that, the load LsT decreases due to the above-mentioned differential characteristic, and a few minutes later, the pressure in front of the adjustment valve P is reduced due to the first-order lag characteristic.
CV rises and load Lsr increases.

Although this ultimately increases the load, it also causes transient load fluctuations.

It should be noted that if the change in the pressure in front of the adjustment valve PCV at loads LUI, LU2, and LU3 is made at a slow rate and the adjustment valve opening degree ACV is changed slowly, it is possible to reduce the load fluctuation range, but if this is adopted, The change in the pressure P in front of the adjustment valve is also delayed, and overall load follow-up is delayed, so this is not an essential solution.

In view of the above, it is an object of the present invention to provide a pressure change control device for a steam turbine that can provide high-speed response without causing the above-mentioned transient load fluctuations.

In the present invention, the turbine load is input, and when the load increases, the pressure PCV in front of the regulator is kept constant, or the regulator valve opening AC is kept constant.
The pressure before the control valve is set so that V is a first constant value, and when the load decreases, the pressure before the control valve PCV is set to be constant, or the control valve opening degree ACV is set to be a second constant value.

As a result, the opening degree of the adjusting valve is not reduced when the load increases, or the opening degree of the adjusting valve is not increased when the load decreases, and transient load fluctuations do not occur.

FIGS. 3A, 3B, and 3C are explanatory diagrams of a pressure change control system for a steam turbine according to the present invention.

As shown in A in the same figure, when the load increases, the adjustment valve opening ACV is fixed at the opening upper limit value AUL, and when the load decreases, the opening lower limit value AUL is fixed.
Let's call it LL.

As a result, the pre-regulator pressure setting value PR is proportionally and continuously changed according to the load L8T of the steam turbine 1.

Note that when the load is changed with a change in opening degree, the pressure PR is kept constant.

The hysteresis width LH of the load LsT is changed according to the load L8T so that it does not become less than the opening lower limit value ALL.

Next, the response of the load Lst and the adjusting valve opening ACV will be explained based on FIGS. 3B and 3C.

Similar to FIG. 2B, FIG. 3B shows the response of the load LsT and the adjustable valve opening ACV during the load increase process, and the differences will be explained below.

In response to the load request LD in the increasing direction, first, the amount of steam generated by the boiler is increased, and the prepressure PCV of the control valve T is accordingly increased.
rises.

The adjusting valve operating device 11 gradually opens the valve 7 in order to keep the pcv constant at P2, and at time t2, the adjusting valve opening ACV reaches AUL.

Thereafter, the pressure setting value PR before the regulating valve is changed proportionally according to the load Lst of the steam turbine 1, and since the boiler generated steam energy and the steam turbine load are maintained in a balanced state, the regulating valve opening ACV is changed to AUL. The stable load L is maintained and the load request LD is maintained as shown in FIG. 3B.
It is possible to follow st.

FIG. 3C shows the response of the load Lst and the adjusting valve opening ACV during the load lowering process.

In response to the load request LD, until time t2, the pressure setting value pR before the regulator valve is lowered with the PH constant pressure state and the load is lowered, so the regulator valve opening ACV decreases to the opening lower limit value ALL as the amount of steam generated by the boiler decreases. do.

After time t2, the pressure setting value PR before the regulating valve changes from PH to PL.
The adjustment valve opening A is changed in proportion to the load until time t3.
Since the CV is maintained at ALL, the load L's'r of the steam turbine 1 is stable as in the above load increase process.
can be lowered.

In addition, in the explanation, the load request LD is given in the form of a ramp, but in normal load operation conditions, the load request LD is a central power supply that is sent to each plant in the power system in consideration of economical operation of the power system. It corresponds to a directive and changes from time to time.

Therefore, as can be seen from the above explanation, in the steam turbine pressure transformation control system according to the present invention in response to increases and decreases in the load request LD, since the hysteresis widths L and H are provided, the change in the adjustment valve opening ACV is caused by the pressure transformation process. Then, the opening upper limit value A
UL or the lower limit value ALL, and in a constant pressure process, the valve will open and close between the upper limit value AUL and the lower limit value ALL, and the valve sticking phenomenon will not occur.

Next, FIG. 4 shows an embodiment of a steam turbine pressure change control device according to the present invention.

A multiplier 21 in the corner of FIG. 4 is for changing the hysteresis width LH according to the load Lst of the steam turbine.
The optimum hysteresis width LH can be set in consideration of the throttle loss and valve sticking phenomenon.

The switch 22 outputs the hysteresis signal LH when the output signal CA of the comparator 25 is "0", and the subtracter 23 outputs the hysteresis signal LH when the output signal CA of the comparator 25 is "0".
Subtraction of st and the output of the switch 22, the adder 24 is the load Ls
t and the output of the switch 22 are added.

The comparator 25 connects the output LA of the subtracter 23 and the analog memory 2.
7's output Lc, and when LA>Lc, the output C
Let A be "1".

The comparator 26 outputs the output B of the adder 24 and the analog memory 2.
7, and when LB≦Lc, the output CB is set to ``1''.

When the output CA of the comparator 25 is "1", the output of the analog memory 27 is increased so that Lc-LA=LsT,
When the output CB of the comparator 26 is "1", the output is decreased to become Lc=LB=LsT=LsT+LH, and CA=
When cB="0", the output is held.

The coefficient setter 28 sets a coefficient so that the opening degree upper limit value AUL is reached when the rated load LmaX, and the high value selector 29 sets the lower limit PL of the pre-regulator pressure setting value.

The operation of the embodiment of the present invention having the above configuration will be explained based on FIG. 3A.

When the load LST of the steam turbine 1 is less than LU1, PR=P
However, in the load increasing process where Lst>Lu1, LA>LC, and in the state of CA="1", the output Lo of the analog memory 27 follows the load LsT.

In this state, cB="0" because LR>Lc.

For example, if the load LsT is settled at Lmax, LsT=L
o (that is, PR-PH), and CA="0", so LA=LsT-LH<Lc, LB=LST+L
When H>Lc, CA="0" and CB="0", output t
,c (i.e., PH) enters the holding state.

Next, when the load drops from this state, Lst=Ll
Until reaching 2, CA="0" and CB="0", so Pr=PH.

Then, when LST<Ll2, cA="o", LB
<Becomes LC, output L.

follows L88=LsT+LH and settles to PR=PL.

As is known from the above, according to the present invention, the following effects can be obtained.

(a) During steam turbine load following operation, the steam turbine load can be stably followed without being affected by changes in the pre-regulator pressure setting value.

(b) Variable pressure operation is possible with a wide range of load levels and a large opening of the regulator, reducing valve throttling loss.
And it can be operated efficiently.

(c) Since a hysteresis width is provided for changes in load, it is possible to prevent the valve from sticking.

(d) The steam turbine pressure change control system of the present invention can be easily configured using conventionally used calculation modules;
There's no problem.

What is shown in FIG. 5A is a modification of the variable pressure control system for a steam turbine according to the present invention.

The hysteresis width LH is made constant regardless of the load I's'r of the steam turbine, and if the multiplier 21 in Fig. 4 is removed, it can be made SR-LH and easily realized. is possible.

FIG. 5B shows the response of the adjusting valve opening ACV and the load L's'r during the load lowering process when using a modification of the present invention.

As the load decreases, the pre-adjustment valve pressure set value is also changed, and at the same time, the adjustment valve opening degree ACV is also gradually narrowed down to the opening degree lower limit value ALL.

In addition, when the load level is high, the variation range of the adjustment valve opening becomes smaller.

Although there is such a difference compared to FIG. 3A, the intended purpose can be achieved.

In the above explanation, the load I's' of the steam turbine 1
Although the pre-regulator pressure setting value PR is changed by r, it is also possible to use the turbine inflow steam flow rate, which is approximately proportional to the load L's'r, instead of the load L's'r.

Actually, the pressure after the first stage of the turbine is used as a signal corresponding to the turbine inflow steam flow rate.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the variable pressure operation method of a steam turbine, Fig. 2 A is a diagram showing the relationship between the pressure setting value before the regulating valve and the load in the conventional variable pressure control method, and Fig. 2 B and C are the loads in this method. A diagram showing the response of load and adjustment valve opening during the rising process, Figure 3A
3B is a diagram showing the relationship between the pressure setting value before the regulating valve and the load in the variable pressure control method of the steam turbine according to the present invention, and FIG. 3B is a diagram showing the response of the load and the variable valve opening in the load increase process in this method , FIG. 3C is a diagram showing the response of the load and control valve opening during the load drop process in this method, FIG. 4 is a configuration diagram showing an embodiment of this method, and FIG. 5A is a diagram showing a steam turbine according to the present invention. FIG. 5B is a diagram showing the response of the load and the opening degree of the adjusting valve in the load lowering process of the modified example of the pressure change control method. 1... Steam turbine, 2... Generator, 3... Condenser, 4
...Water pump, 5...Boiler, 6...Fuel valve, 7...
Regulating valve, 8...Load detector, 9...Pressure detector in front of regulating valve, 10...Function generator, 11...Adjusting valve operator, Lst
...Steam turbine load, PR...Pressure setting value before regulating valve,
PCV...pressure before regulating valve, 21...multiplier, 22...switcher, 23...subtractor, 24...adder, 25, 2
6... Comparator, 27... Analog memory, 28... Coefficient unit, 29... High value selector, SH... Hysteresis setting value.

Claims (1)

[Claims] 1. A steam generation source that generates steam; a steam turbine driven by the steam from the generation source; and a control device provided between the turbine and the steam generation source to adjust the flow rate of steam. Valve: A control valve operator that changes the pressure in front of the control valve; Provided between the control valve and the steam generation source, detects the pressure in front of the control valve and outputs a signal to the control valve operator. a pressure detector in front of the regulating valve; which receives a signal corresponding to the load of the steam turbine as input, sets and outputs a pressure setting value in front of the regulating valve proportional to the input, and generates a function that provides the output to the operating device; A steam turbine pressure transformation control device comprising: 2. In the pressure change control device for a steam turbine according to claim 1, when setting the pressure setting value before the regulating valve, there is a difference between the pressure setting value before the regulating valve and the steam turbine load or the flow rate of steam flowing into the turbine. A steam turbine pressure transformation control device characterized by having a hysteresis width.