JPH0158322B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a turbine control device, and in particular, when a set load signal at the time of load cutoff is larger than a turbine actual output signal by a certain value or more, a steam control valve (hereinafter referred to as
This invention relates to an electro-hydraulic turbine control device that can quickly close an intermediate check valve (hereinafter referred to as a CV) and an intermediate check valve (hereinafter referred to as an IV).

Generally, during normal operation of a turbine that uses an electro-hydraulic turbine control device,
That is, turbine speed control and load control during load operation are performed by coordinated opening/closing control of CV and IV. In other words, during normal operation, IV
is always fully open, and load changes and minute changes in frequency are controlled by the CV opening degree. Also, when the speed suddenly increases due to load shedding, the CV closes in advance as the speed increases, and the CV The IV starts closing operation only when it reaches near full open.

Figure 1 shows a block diagram of a turbine control device equipped with CV and IV control circuits that has been conventionally used to perform such operations. In the figure, a represents the difference between the turbine set speed and the actual speed. The turbine speed deviation signal 2 amplifies the speed deviation signal a so as to multiply the turbine speed deviation signal a by a first coefficient consisting of the reciprocal of the CV speed regulation rate _RCV .
A coefficient unit 3 serving as a first calculation unit outputting a CV speed deviation signal b outputs a turbine speed deviation signal a;
The turbine speed deviation signal a is amplified so as to be multiplied by a second coefficient which is the reciprocal of the IV speed regulation rate R _IV .
A coefficient unit as a second calculation unit that outputs the IV speed deviation signal c, d is a set load signal, and 7 is a coefficient that adds the CV speed deviation signal b and the set load signal d.
An adder that outputs a CV flow rate signal g; 8 is a coefficient unit that multiplies the set load signal d by a third coefficient to be described later; and f is a third calculation unit that outputs an IV load bias signal e; f is an IV full-open bias The signals 10 are the IV speed deviation signal c, the IV load bias signal e,
The IV flow rate signal h is obtained by adding the IV full-open bias signal f.
14 is a CV opening control unit that outputs a CV opening signal i according to the CV flow rate signal g;
15 is an IV opening signal j for the IV flow rate signal h.
This is an IV opening control section that outputs.

In this configuration, the speed deviation signal a is amplified by the coefficient multipliers 2 and 3 according to the CV speed adjustment rate and the IV speed adjustment rate, and is sent to the adder 7, as the CV speed deviation signal b and the IV speed deviation signal c, respectively. 10
is input to. By the way, the CV speed adjustment rate is normally set to 5% and the IV speed adjustment rate is set to 2%. on the other hand,
The set load signal d is input to an adder 7 and a coefficient unit 8. The coefficient of the coefficient multiplier 8 is set to a value as shown in equation (1), and the set load signal d is multiplied by this coefficient,
It is applied to the adder 10 as the IV load bias signal e.

Coefficient = R _CV /R _IV (1) Here, R _CV is the CV speed adjustment rate, R _IV is the IV speed adjustment rate, and in the coefficient units 2 and 3, the speed deviation a is multiplied by 1/R _CV and 1/ It is assumed that an operation is performed to multiply R _{by IV} . On the other hand, the IV is fully open to the adder 10 even when there is no load.
IV full-open bias signal f is input. The outputs of the adders 7 and 10 are CV flow signals g and IV, respectively.
The flow rate signal h is input to the CV opening control section 14 and the IV opening control section 15. The respective output signals of the CV opening degree control section 14 and the IV opening degree control section 15 are expressed as a CV opening degree signal i and an IV opening degree signal j.
CV and IV are given to drive these.

Fig. 2 is a characteristic diagram showing control operations of CV and IV during turbine overspeed control in the turbine control device shown in Fig. 1, and the vertical axis is the CV flow signal g and IV.
The flow rate signal h is shown, and the horizontal axis shows the turbine speed k.

Here, when the turbine speed k becomes the set speed 1 or higher, the CV flow rate signal g first decreases along the broken line in the figure, and at the CV no-load position speed m, the CV flow rate signal g becomes a flow rate signal equivalent to the no-load flow rate. becomes. If the turbine speed k further increases, the IV flow rate signal h
decreases along the solid line in the figure, and at the IV fully closed speed n, the IV flow rate signal h becomes a flow signal corresponding to the IV fully closed position.

Such an operation is possible because the coefficient unit 8 is set with a coefficient that takes a value as shown in equation (1). The reason is as follows. Now, if we express the signals g and h in Fig. 1 using the formula, g=d-a/R _CV (2) h=d×(R _CV /R _IV )-(a/R _IV )+1 (3) Become. Here, since the turbine speed when the signal g becomes 0 is m (that is, point m in Fig. 2),
In equation (2), when g=0 and a=ml, 0=d-(ml)/R _CV (4), then R _CV =(ml)/d (5) is obtained. By substituting this value of R _CV into equation (3), we obtain h=(1/R _IV )(ml-a)+1 (6). From equation (6), when the speed deviation signal a is ml (i.e., at the point where CV is fully closed), h is 1 (i.e., IV is fully open), and the speed deviation signal a
It can be seen that h becomes 0 when is ml+R _IV . As a result, characteristics as shown by the solid line in FIG. 2 are obtained.

Incidentally, in recent years, an increasing number of power plants are implementing variable voltage operation in order to improve the function of thermal power plants as intermediate load thermal power plants. This variable voltage operation has the effect of improving the plant's start/stop characteristics, load following function, etc., so its introduction is highly useful.

FIG. 3 is a characteristic diagram showing a typical variable pressure operation method, in which the horizontal axis represents the actual turbine output signal p, and the vertical axis represents the main steam pressure q. In this case, the main steam pressure q is constant at the rated pressure v at a load between the rated output r and the variable pressure limit high load s, as in a normal constant pressure plant. However, as shown in the figure, at a load between the high load of the transformation pressure limit s and the low load of the transformation pressure limit t, the main steam pressure q changes from the rated pressure v to the boiler minimum pressure w, and the load changes accordingly. At a load below the pressure transformation limit low load t, the main steam pressure q is kept constant at the boiler minimum pressure w.

Figure 4 shows the actual turbine output signal p and set load signal d when performing variable pressure operation as shown in Figure 3.
FIG.

That is, since the main steam pressure q is constant when the actual turbine output p is between the rated output r and the high pressure transformer load s, the set load signal d is changed between the rated load x and the high load y. but,
The main steam pressure q changes as shown in Figure 3 between the high load at the transformer limit s and the low load at the transformer limit t, and the load changes accordingly, so the set load signal d remains almost constant at the set transformer limit high load y. becomes. Since the main steam pressure q is constant when the turbine actual output signal p is below the pressure transformation limit low load t, the set load signal d is changed as shown in FIG. By the way, the two-dot chain line in the same figure is the set load signal d in a normal constant pressure plant.
The relationship between the actual turbine output signal p and the actual turbine output signal p is shown.

As is clear from FIG. 4, in variable pressure operation, when the turbine actual output signal p is below the variable voltage limit low load t, the set load signal d becomes higher than the turbine actual output signal p. Normally, in a constant pressure plant, the turbine actual output signal p and the set load signal d are equal, so this is one of the characteristics of variable pressure operation.

As described above, the following differences in control arise between constant pressure plants and variable pressure plants.
In other words, regarding turbine overspeed control, constant pressure plants perform CV and IV closing operations as shown in the characteristic diagram in Figure 5, while transformer plants exhibit closing operation control characteristics as shown in the characteristic diagram in Figure 6. .

Here, the broken line is a graph showing changes in the CV flow rate signal g, and the solid line is a graph showing changes in the IV flow rate signal h, the vertical axis shows the values of the signals g and h, and the horizontal axis shows the value of the turbine speed k.
As shown in Fig. 4, in a region where the actual turbine output is less than or equal to s (a region where the set load signal d is larger than the actual turbine output signal p), the set load signal d is set at a constant pressure in variable pressure operation (solid line in Fig. 4). Operation (Figure 4 double-dashed line)
Become bigger. Even if the turbine speed is the same k=l, the set load signal d is different as described above.
Therefore, the point m where the CV flow rate signal g (broken line in the figure) becomes 0 is different between FIG. 5 and FIG. 6.

That is, as explained in FIG. 2, the IV flow rate signal h begins to decrease when the turbine speed is m, when g=0, and reaches 0 when the turbine speed is n.
becomes. Therefore, first, as is clear from equation (4) or equation (5), the turbine speed m when g=0
is m=dR _CV +l (7), and in equation (3), h=0, a=n−
If we put it as l, then the turbine speed n when h=0
is n=dR _CV +R _IV +l (8).

In this way, m, n shown in FIGS. 5 and 6
is expressed as in equations (7) and (8). Since the set load signal d in the variable pressure operation in FIG. 6 is larger than the set load signal d in the constant pressure operation in FIG. 5, the turbine speeds m and n are larger in the variable pressure operation than in the constant pressure operation. In variable pressure operation, the turbine speed increases when CV and IV are fully closed than in constant pressure operation. This means that when controlling a transformer plant using a conventional turbine control device,
CV after load shedding compared to constant pressure plant control,
This means that the action of closing the IV will be slower.
Therefore, there is a problem in that a sufficient effect of preventing overspeed due to load shedding cannot be obtained.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a turbine control device that can ensure quick CV and IV closing operations during load shedding even during variable pressure operation of the turbine.

More specifically, the present invention detects the deviation between the set load and the actual turbine output at the time of load interruption, and if the set load is larger than the actual turbine output by a certain value or more, the deviation is detected.
By varying the CV speed regulation rate and making the CV no-load position speed equal to that of a constant pressure plant,
The objective is to provide a new turbine control device that realizes rapid closing response of CV and IV.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 7 is a block diagram of a turbine control device according to an embodiment of the present invention, in which A is a turbine actual output signal, B is a constant level signal, and 33a and 33b are the turbine actual output signal A and constant level signals. Relay contacts that switch B, 33c and 33d are set load signal d
34 is the relay contact 33a, 33b, 33c, 33d which switches the constant level signal B.
36 is a CV adjustment rate calculating section which calculates a CV adjustment rate signal C from the input signal from the input signal and the turbine speed deviation signal a, and outputs a CV speed deviation signal b; IV as the third calculation unit that calculates the signal e
This is a load bias signal calculation section. Incidentally, the relay contacts 33a, 33b, 33c, and 33d are driven by the same relay (not shown);
3c constitutes a normally closed contact, and 33b and 33d constitute a normally open contact.

That is, normally, the constant level signals B and B are given to the calculation unit 34 via the contacts 33a and 33b, and when the set load signal d becomes somewhat larger than the turbine actual output signal A, the relay is switched and the contacts are closed. The turbine actual output signal A and the set load signal d are provided to the calculation section 34 via 33b and 33d. The difference between the configuration in FIG. 7 and the configuration in FIG. 1 is that it has a turbine actual output signal A and a constant level signal B as new inputs to the CV and CI control circuits. 3
3b, 33c, and 33d, and the signals selected by relay contacts 33a, 33b, 33c, and 33d are input to the CV adjustment rate calculation section 34,
Here, the CV adjustment rate signal C and the CV speed deviation signal b are calculated, while the CV adjustment rate signal C is input to the IV load bias signal calculation section 36, where the IV load bias signal e is calculated.

FIG. 8 is a block diagram showing details of the CV adjustment rate calculating section 34 in FIG _.
39 is a divider for dividing the amplified signal E by the turbine actual output signal A or constant level signal B selected by the relay contacts 33a and 33b; 40 is the output of the divider 39; Relay contact 3
Setting load signal d selected by 3c and 33d
Alternatively, a multiplier 38 multiplies the constant level signal B and outputs it as a CV speed deviation signal b; It is a calculator.
Note that the amplifier 37, the divider 39, and the multiplier 40 function as a first calculation section.

In this configuration, the speed deviation signal a is amplified by the coefficient multiplier 37 according to the conventional CV adjustment rate to become the amplified signal E. The amplified signal E is transmitted through the relay contact 33
The set load signal d or constant level signal B is divided by the divider 39 by the turbine actual output signal A or constant level signal B selected by a, 33b, and further selected by the relay contacts 33c, 33d.
is multiplied by the multiplier 40. Its output signal is CV
The signal becomes the speed deviation signal b and is input to the adder 7.

On the other hand, the speed deviation signal a is divided by the CV speed deviation signal b by a divider 38 to obtain a CV adjustment rate signal C.

FIG. 9 is a block diagram showing details of the IV load bias signal calculation section 36 in FIG. This is a multiplier that multiplies the output of the device 41 by the CV adjustment rate signal C and outputs the IV load bias signal e.

In such a configuration, the operation under normal conditions, that is, when the actual turbine output p and the set load d are approximately equal, will be described first. In this case, the constant level signal B is applied to both the divider 39 and the multiplier 40 in FIG. 8 by the action of the relay. After division by B, multiplication by B is performed, so the signals b and C become as follows.

b=a/R _CV (9) C=R _CV (10) On the other hand, in FIG. 9, the coefficient multiplier 41 performs an operation that is multiplied by 1/R _IV , similar to the coefficient multiplier 3 of the conventional device shown in FIG. After all, the signal e becomes e=d(R _CV /R _IV ) (11). Thus, the signal b of the device shown in FIG.
It can be seen that during normal operation, the signals e and e exhibit the same values as these signals of the device shown in FIG. 1, and the device operates in the same way as the device shown in FIG.

However, when the set load signal d becomes larger than the actual turbine output signal A by a certain value or more during the operation of the transformer plant, the function of the relay causes the divider 39 and multiplier 40 in FIG. ,
A turbine actual output signal A and a set load signal d are respectively given. In the end, signals b and C become as follows.

b=(d/A)・a/R _CV (12) C=(A/d)・R _CV (13) Therefore, the signal e is e=(A/d)・d(R _CV /R _IV ) (14). In this way, in the operation when the set load signal d becomes larger than the actual turbine output signal A by more than a certain value, the value of the signal b becomes (d/A) times as much as in the normal operation. It can be seen that the signal e is also multiplied by (A/d).

In other words, this means that the first coefficient (1/R _CV ) is modified in a direction that increases the value of the CV speed deviation signal b, and at the same time, the third coefficient is modified in a direction that decreases the value of the load bias signal e. (R _CV /R _IV ), which increases the ratio of the CV closing operation amount to the increase in turbine speed k,
As the CV closing operation begins to occur rapidly,
As a result, the starting point of the IV closing operation is brought forward.

Here, in each transformer plant shown in Figure 11,
The turbine speed m at the completion of the CV closing operation (that is, the start of the IV closing operation) and the turbine speed n at the completion of the IV closing operation are determined as follows.

First, the signals g and h in FIG. 7 are _expressed as follows: g=d-(d/A)×(a/R _CV ) (15) _IV ) −(a/R _IV )+1 (16). Here, g = 0, a = ml according to the formula (15)
0=d-(d/A)×((ml)/R _CV ) (17) From (17), m=AR _CV +l (18) Also, h=0, a=n-l can be written as Substituting into (16), 0=A/d×d×(R _CV /R _IV ) −((n-l)/R _IV )+1 From (19), n=AR _CV +R _IV +l (20) Become.

Since m and n in the transformer plant in Fig. 6 are as shown in equations (7) and (8) as already determined, comparing this with m and n in the transformer plant in Fig. 11, Since d>A, dR _CV > AR _CV , and according to the transformer plant of FIG. 11 (i.e., this example), the turbine speed is lower than that of the transformer plant of FIG. 6 (i.e., the conventional). This completes the closing operation of CV and IV. Therefore, if the control characteristics as shown in FIG. 6 are obtained in normal operation, in the operation where signal b is multiplied by (d/A), the first
Control characteristics as shown in Figure 1 are obtained. The slope of the dashed line representing the signal g becomes (d/A) times steeper.

Figure 10 shows relay contacts 33a, 33b, 33
This is a circuit configuration diagram showing the details of the actual load-set load imbalance control section that switches between the relays 33c and 33d.Relay contacts 33a and 33c are closed when the relay 33 is not energized and open when the relay 33 is energized; Contacts 33b, 33d, and 33e are configured to perform the opposite operation. Contact 42 is normally open and closes when the main circuit breaker opens and is disconnected from the grid, contact 43 detects turbine acceleration and closes when the acceleration exceeds a certain value, and contact 44 detects the set load signal d. The turbine actual output signal A is compared, and the contact 45 is closed when the set load signal d becomes larger than the turbine actual output signal A by a certain value or more, and the contact 45 is normally closed and opens when the speed increase is suppressed and a settling state is entered. do.

According to this configuration, if a load cutoff occurs when the set load signal d is larger than the actual turbine output by a certain value or more in the turbine that is performing variable pressure operation, the contacts 42, 43, and 44 are all closed, so that the relay 33 is closed. is energized and setting 33e is closed, so relay 33 is held in the energized state until contact 45 opens.

Therefore, if the set load signal d at the time of load cutoff is larger than the turbine actual output signal A by a certain value or more, the relay 33 is energized, so the contact 33
b and 33d are closed, and the set load signal d and the actual turbine output signal A are input to the CV adjustment rate calculation section 34.
The new CV adjustment rate C calculated there is input to the IV load bias signal calculation section 36, and a new IV load bias signal e is calculated. As a result of these operations, the closing operations of CV and IV are performed more quickly as shown in the characteristic diagram of FIG. 11, and turbine overspeed is suppressed. After turbine overspeed suppression, the conventional
Since the CV adjustment rate is desirable, the contact 45 shown in FIG. 10 is opened to release the excitation of the relay 33 and return to the normal state.

As described above, in the present invention, when the set load signal becomes larger than the actual turbine output by a predetermined value or more after load interruption, the turbine speed deviation signal is The first coefficient for determining the steam regulating valve speed deviation signal is modified in a direction that increases the steam regulating valve speed deviation signal, so that the ratio of the closing operation amount of the steam regulating valve to the increase in turbine speed increases. At the same time, the third coefficient for determining the load bias signal from the set load signal is modified in the direction that the load bias signal becomes smaller, so that the closing operation start point of the intermediate check valve is brought forward. Therefore, when the set load signal at the time of load cutoff is greater than a certain value by the turbine actual output signal, CV and IV can be quickly closed, which is extremely effective in preventing turbine overspeed, especially when changing pressure It is possible to obtain a turbine control device that can be effectively applied in plants.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional turbine control device, Figure 2 is a CV during turbine overspeed control,
IV closed operation characteristic diagram, Figure 3 is a characteristic diagram showing an example of the relationship between turbine actual output and main steam pressure in variable pressure operation, and Figure 4 is a characteristic diagram showing the relationship between turbine actual output and set load in variable pressure operation and constant pressure operation. Characteristic diagram shown,
Fig. 5 is a CV and IV closing operation characteristic diagram during turbine overspeed control in a constant pressure plant, and Fig. 6 is a CV and IV closing operation characteristic diagram during overspeed control in a variable pressure plant at the same actual turbine output as in Fig. 5. FIG. 7 is a block diagram of a turbine control device according to an embodiment of the present invention, FIG. 8 is a block diagram of the CV adjustment rate calculation section of FIG. 7, and FIG. 9 is a block diagram of the IV load bias signal calculation section of FIG. 7. 10 is a circuit configuration diagram showing the actual load-set load imbalance control section applied to the configuration in FIG. 7, and FIG. 11 is a CV during overspeed control in the configuration in FIG. 7. It is an IV closing operation characteristic diagram. 3... Coefficient unit (second calculation unit), [37... amplifier, 39... divider, 40... multiplier] (first calculation unit), [41... amplifier, 46... multiplication vessel〕
(Third calculation unit), 14...Steam control valve speed control unit, 15...Intermediate check valve speed control unit, 33...The set load signal d is larger than the actual turbine output signal A by a certain value or more, and the turbine is Relays 33a to 33d for detecting a load shedding state...
... Relay contact for switching inputs to the divider 39 and multiplier 40, 38... Divider (first coefficient and third coefficient correction means), a... Turbine speed deviation signal, b... Steam control valve speed deviation signal,
c...Intermediate check valve speed deviation signal, d...Setting load signal, e...Load bias signal, f...Intermediate check valve fully open bias signal, g...Steam control valve flow rate signal, h...Intermediate check valve flow rate Signal, i...Steam control valve opening signal.

Claims (1)

[Scope of Claims] 1. A first calculation unit that calculates a steam control valve speed deviation signal by multiplying a turbine speed deviation signal by a first coefficient; a second calculation unit that calculates a speed deviation signal; a third calculation unit that calculates a load bias signal by multiplying a set load signal by a third coefficient; , a steam regulating valve opening degree control section that controls the opening degree of the steam regulating valve; and an intermediate check valve opening degree control unit that controls the opening degree of the intermediate check valve based on the intermediate check valve speed deviation signal and the load bias signal. In a turbine control device that controls a turbine after load interruption, when the set load signal becomes larger than the actual output of the turbine by a predetermined value or more, the set load signal and the turbine According to the value of the ratio to the actual output, the first coefficient is modified in a direction in which the value of the steam control valve speed deviation signal increases, and at the same time, the third coefficient is modified in a direction in which the value of the load bias signal decreases. A turbine control device further comprising means for modifying.