JPS6032083B2 - Boiler feed pump control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a boiler that can perform stable water supply control using a turbine bed water pump, even in the face of large and rapid fluctuations in the amount of water supplied, such as in-plant load runbacks. This invention relates to a water pump control device.

In thermal power plants, water is usually supplied by a turbine-driven water pump or a motor-driven water pump.

However, when an in-plant load runback occurs, conventionally, in a thermal power plant combined with a supercritical pressure boiler equipped with a boiler circulation pump (hereinafter referred to as BCP equipped), the turbine-operated feed water pump that had been in operation is tripped, and the motor The water supply is controlled by the on-site water supply pump during load runbacks within the station.

This means that the minimum flow rate of the boiler feed pump is approximately 15% at the rated time.
%, whereas the water supply flow rate of a supercritical pressure boiler with 8CP during in-house load runback is as low as about 5% to 10% of the rated value, so the advantages of a supercritical pressure boiler with BCP can be utilized during in-house load runback. This is because if you try to make it work, the amount of water supply change will be sudden and very large, which is difficult to control with a turbine-driven water supply pump. Furthermore, this BCP
As mentioned above, the supercritical pressure poller has economically advantageous advantages such as low superdynamic loss, although it is difficult to control the water supply during in-house load runback. On the other hand, supercritical pressure boilers that do not have a boiler circulation pump (hereinafter referred to as "without BCP") have a relatively large maximum flow rate of approximately 25% of the rated value.
During plant load runback, as in normal operation, water supply control by the turbine-operated water supply pump is performed to some extent, although it is insufficient.

Conventionally, in the case of a power generation plant combined with a supercritical pressure boiler without BCP, water supply control during in-house load runback is performed as follows.

That is, due to the occurrence of load runback within the station, one of the two turbine-operated water pumps (designated A) that had been in operation until then is tripped, and the remaining one (designated B) is tripped. Switching to control using program signals. As shown in FIG. 1, the control of the turbine-operated water supply pump B involves changing the water supply demand 1 using a program generator after the occurrence of an in-house load runback, and calculating the difference 4 from the water supply flow rate 3 using the controller 5. The applied signal 6 and the suction flow rate 7 of the turbine water supply pump B
is calculated by a calculator 8 and adjusted by a regulator 9 to obtain a water supply control signal 10, thereby generating a governor input signal for the turbine bed water pump B. Water supply control using the conventional turbine-driven water supply pump as shown in Fig. 1 above is not possible in thermal power plants that are combined with supercritical pressure pumps with BCP. There is a drawback that it cannot be done.

If a motor-operated water pump is used instead of the turbine-operated water pump, it will be necessary to increase the capacity of the transformer, resulting in higher costs. For this reason, there is a strong demand from customers to be able to perform water supply control using turbine dynamic water supply pumps during station load runback. On the other hand, in the case of a thermal power plant that is combined with a supercritical pressure pump without BCP, the water supply is controlled by a turbine-driven water pump during internal load runback using the control system shown in Figure 1. Due to the transmission delay in the control system, there is a drawback that rapid fluctuations such as in-station load runback cannot be adequately followed.
Furthermore, when the water supply flow rate during in-house load runback is as low as 5 to 10% of the rated value, such as in a supercritical pressure boiler with BCP, it seems impossible to use the control system shown in Figure 1. . The present invention has been made in view of the above points, and includes introducing a deviation signal, an in-house load runback state signal, and a tracking signal into a regulator through an adjustment calculator for a water supply flow rate request signal and an actual water supply flow rate signal, The first system that sends this regulator output signal to the main switch, and the signal setting device that sets the FWC signal increase rate, and the increase rate setting device that controls the FWC signal after the occurrence of internal load runback, and after the set time ti. The output signal of each timer that converts from the "0" level to the "1" level is introduced into an addition/subtraction calculator via a switch circuit, which is located downstream of the timer and is equipped with a switch that opens and closes depending on the output signal of the timer. , and the setting value of the integrator upper limit setter is input to the integrator with upper limit value setter, and its output signal and the output signal of the initial FWC signal setter at the time of station load runback are input to the main addition/subtraction calculator. A second system is provided for sending the output signal of the calculator to the main switching device, and the main switching device selects the output signal of the main addition/subtraction calculator when the station load runback status signal is at the “1” level, By selecting the above-mentioned regulator output signal and supplying water that instantly responds to the change when the water level is 100%, it is possible to prevent large and rapid changes in water supply, such as during station load runback. It is an object of the present invention to provide a control device for a boiler feed water pump that is capable of controlling water supply by a turbine-operated feed water pump even in such cases and has high controllability.

Next, an embodiment of the boiler feed pump control device of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing one embodiment. In this figure 2, 1
1 is a water supply flow rate request signal, and 12 is an actual water supply flow rate signal. This water supply flow rate request signal 11 and the actual water supply flow rate signal 12 are introduced into a calculator 13, where they are calculated and a deviation signal is obtained. The signal is sent to the regulator 14. A regulator output signal 15 is sent from the output side of the regulator 14 to a switch 16, and the switch 16, which will be described in detail later, sends a feed, water, and water signal from its output side.
A control signal 17 (hereinafter referred to as the FWC signal) is input to a governor 18 for operating the turbine water feed pump.

Further, a tracking signal 19 is sent to the regulator 14 from the output side of the switch 16, and furthermore, when a station load runback occurs, a station load runback status signal 20 (hereinafter referred to as an FCB status signal) is provided. is also adapted to be introduced into the regulator 14. This FCB status signal 20 is a binary signal of high level "1" or low level "0", and is normally at the "0" level, and becomes the "1" level when an internal load runback occurs.

This FCB status signal 20 is also sent to the timer 21 and the switch 16, and the switch 16
An output signal 23 from the main addition/subtraction calculator 22 is also introduced.

The regulator output signal 15 is sent from the output side of the regulator 14 to the switch 16 so that the regulator 14 outputs the FWC signal 17 by the tracking signal 19 when the FCB status signal 20 is at the "1" level. It looks like this.

In other words, the tracking signal 19 tracks the regulator output signal 15 from the regulator 14 to the FWC signal 17 of the switch 16 (
The tracking operation is performed using the FCB status signal 20 which is a control input of the switch 16.
It is configured such that it is performed only while the signal is at the "1" level and becomes the output signal 23 from the main addition/subtraction calculator 22.

On the other hand, 24 is an initial FWC signal setting device at the time of FCB,
Output signal 2 of the initial FWC signal setter 24 during this FCB
5 and an output signal 27 of the integrator with upper limit value setter 26 are sent to the main addition/subtraction calculator 22. Also,
28 is a zero signal setter that sets the FWC signal increase rate to zero, and 29 is a post-FCB FWC signal increase rate setter (hereinafter referred to as an increase rate setter).

Output signal 30 of zero signal setter 28 and increase rate setter 2
The output signal 31 of the timer 9 is sent to a switch 32, and the output signal 33 of the timer 21 described above is also introduced to the switch 32. Timer 21 is FC
After the B state signal 20 becomes the "1" level, the output signal 33 is changed from the "OJ level" to the "1" level after a preset time ti, and therefore the output signal 33 of the timer 21 becomes the "1" level. ” level or “0” level binary signal.

When the output signal 23 of the timer 21 reaches the "1" level, the output signal 36 of the switch 32 is switched from the output signal of the koto signal setter 28 to the output signal 31 of the increase rate setter 29. The output signal 33 of the timer 21 controls on/off of the switch 34.
4 is a gate when the output signal 33 of the timer 21 is at the "1" level, and is closed when the output signal 33 is at "0".

This switch 34 is connected between the output side of the integrator with upper limit value setter 26 and a computing unit 35.
The output signal 36 of the switch 32 is also introduced into the input circuit 32, and the output signal 37 of the arithmetic unit 35 is sent to the input side of the integrator 26 with an upper limit value setter.

The integrator with upper limit value setter 26 receives the output signal 37 of the arithmetic unit 35.
is integrated with respect to time and sent to the main addition/subtraction calculator 22 as an output signal 27, but the integrated value is limited by a value set in advance by an integrator upper limit setter 38. It's summery.

The arithmetic units 13, 22, and 35 follow the addition or subtraction signals shown in the figure, the arithmetic unit 13 subtracts "signal 11 - signal 12", and the main addition/subtraction arithmetic unit 22 adds and calculates "signal 25 plus signal 27". The switch 35 has a function of subtracting "signal 36 - signal 27", and the switch 16 selects the output signal 23 of the computing unit 22 when the FCB status signal 20, which is the control input signal, is at the "1" level. Priority is given to output signal 17, and F
When the CB status signal 20 is at the "0" level, the regulator output signal 15 is output as the output signal 17.

Also, the switch 32 indicates that the output signal 33 of the timer 21 is "1".
When the level is set, the output signal 31 of the increase rate setter 29 is output as the output signal 36, and the output signal 33 of the timer 21 is "
0'' level, the output signal 30 of the zero signal setter 28 is output as the output signal 36.

Next, the water supply of the boiler feed pump control device of the present invention configured as described above will be explained.

First, during normal operation, the FCB status signal 20 is "0".
Therefore, the switch 16 has been switched to the regulator 14 side, and the regulator 14 is operating normally.

That is, the water supply flow rate request signal 11 and the actual water supply flow rate signal 12 are calculated by the calculator 13, and the deviation signal thereof is introduced into the regulator 14 and adjusted, and then the regulator output signal is output from the output side of the regulator 14. 15 is introduced into the switching device 16, and from the output side of this switching device 16, an input signal of the turbine-operated water pump operating governor 18, that is, an FWC signal 17 is input.
is output as In this case, the same feedback control of water supply as conventionally performed is performed, and the FWC signal 17 in this case corresponds to the characteristic a in FIG. 3A.

In this state, when the FCB status signal 20 is generated,
Upon receiving an external force that causes this FCB status signal 20 to go to the "1" level, the switch 16 switches to the main addition/subtraction calculator 22 side,
The output signal 23 of the main addition/subtraction calculator 22 is selected by the switch 16.

The output signal 23 of the main addition/subtraction calculator 22 is the initial output signal 25 of the WC signal setter 24 and the integrator 2 with upper limit value setter.
However, at this point, the output signal 27 of the integrator with upper limit value setter 26 is "0".
held at the level. Therefore, in this case, the output signal 25 of the initial FWC signal setter 24, that is, the initial FWC signal
The WC signal setting value is output as an output signal 23 of the main addition/subtraction calculator 22. Then, the output signal 23 of this main addition/subtraction calculator 22 is selected by the switch 16 as described above, and F
The signal becomes a WC signal 17 and is sent to a governor 18 for operating the turbine moving body water supply pump. As a result, the governor valve of the turbine power feed water pump operating governor 18 quickly reaches the required minimum opening degree. The FWC signal 17 in this case is a part of characteristic b in FIG. 3A.

Thereafter, when the time set in advance by the timer 21 has elapsed, the output signal 33 of the timer 21 changes from the "0" level to the "1" level, and the output signal 31 of the increase rate setter 29 passes through the switch 32 and switches to the switch. 32 becomes an output signal 36 and is sent to the arithmetic unit 35.

At this time, since the output signal 33 of the timer 21 is at the "1" level, the switch 34 is opened by this output signal 33, so the output signal 36 of the switch 32 is
5, it becomes an output signal 37 of the arithmetic unit 35 and is input to the integrator 26 with an upper limit value setter.

As a result, the time integral value of the output signal 36 of the switch 32 is sent to the main addition/subtraction calculator 22 as the output signal 27 of the integrator 26 with upper limit value setter.

The calculator 22 includes an initial FWC signal setter 24 at the time of FCB.
An output signal 25 (constant value signal) from is also applied,
The output signal 27 of the integrator with upper limit value setter 26 is added to this output signal 25.

The result of this addition is sent to the switching device 16 as the output signal 23 of the main addition/subtraction calculator 22, and is further sent as the FWC signal 17 from the output side of the switching device 16 to the governor 18 for operating the turbine dynamic feed water pump. .

In this case, the FWC signal 17 changes as shown by characteristic c in FIG. 3A. Since the output signal 27 of the integrator with upper limit value setter 26 is saturated at the upper limit value given by the integral upper limit setter 38, when this output signal 27 reaches the upper limit value, from then on, the FWC signal 17 is Like the characteristic d in Figure A, it maintains a constant value.

As shown in characteristics a to d in FIG. 3A, FWC
Signal 17 ensures the necessary water supply when a load runback occurs in the station, and after reaching a stable steady state as shown in characteristic e in Figure 3B, operators can turn on the FCB as necessary.
If the status signal 20 and timer 21 are reset, the FW
The C signal 17 becomes the regulator output signal 15, which is a feedback control signal during normal operation, and the previous FWC signal 1.
7 is tracked by the regulator 14, the feedforward control is switched to the feedback control bumplessly. The above figure 3B is a FW as shown in figure 3A.
Changes in the water supply flow rate when the C signal 17 is applied to the turbine bed water pump operating governor 18 are experimentally determined by simulation, and Fig. 3C shows the boiler inlet pressure (corresponding to the pump outlet pressure). The change in main steam pressure (corresponding to the feed water pump drive turbine inlet pressure) was experimentally determined through simulation.

In this Figure 3C, the axis f, , , indicates the boiler inlet pressure, and the axis 9 indicates the main steam pressure, and the boiler inlet pressure f, , the main steam pressure 9 is the pressure at the time of local load runback. Even at low temperatures, stable in-house load runback operation can be performed without significantly reducing the boiler inlet pressure.

As mentioned above, in the embodiment of FIG. 2, feedforward control is performed and the feedforward signal is
Considering the changes in boiler input pressure and main steam pressure shown in Figure C, as shown in characteristic b-characteristic c-characteristic d in Figure 3A,
By generating the program, a satisfactory water supply flow rate can be obtained as shown by the solid line in Figure 3B, and stable in-house load runback operation can be achieved without reducing the boiler inlet pressure too much as shown in Figure 3C. can be done. Now, FIG. 4 is a block diagram showing another embodiment of the boiler feed pump control device of the present invention, and this FIG.
Only the parts that are different from the illustrated embodiment are shown, and in FIG. 4, the same reference numerals as in FIG. 2 indicate the same parts.

In FIG. 4, 39 is a water supply return flow rate setting device, which is used in place of the water supply flow rate increase rate setting device 29 in FIG.

The output signal 40 of this water supply return flow rate setting device 39 is
2. The output signal of the switching device 32 is introduced into the first-order delay element 41,
This first-order lag element 41 is configured to have a first-order lag time constant set by a time constant setter 42 .

The output signal 27 of the first-order delay element 41 is sent to the arithmetic unit 22.

That is, in the case of the embodiment of FIG. 4, the first-order delay element 41 and the time constant are used instead of the arithmetic unit 35, the integrator with upper limit value setter 26, and the integrator upper limit value setter 38 in the embodiment of FIG. The setting device 42 is used and, as mentioned above,
In place of the increase rate setting device 29, a water supply return flow rate setting device 39 is used.

By doing this, the same FWC signal as in the embodiment shown in FIG.
9 output signals 40 are added to the step where a predetermined 1
The output signal 27 is sent from the first-order delay element 41 to the arithmetic unit 22 with the next delay.

As a result, the main addition/subtraction calculator 22 uses the initial FW at the time of FCB.
This first-order delay element 4 is applied to the output signal 25 of the C signal setter 24.
1 output signal 27 is added, and the addition result is sent from the output side of the main addition/subtraction calculator 22 as the output signal 23 to the switch 16 shown in FIG.
A governor 18 for operating a turbine-driven water pump as a signal 17
sent to.

The FWC signal 17 obtained in the embodiment of FIG. 4 changes as shown by the solid line in FIG.

The dotted line in FIG. 5 shows the FWC signal in the case of the embodiment of FIG. The rate of change (time constant) of the FWC signal can be set using the time constant setter 42. Everything else other than the above is the same as the embodiment shown in FIG. 2, and in the embodiment shown in FIG. 4, almost the same FWC signal as in the embodiment shown in FIG. This embodiment can achieve almost the same effect as the embodiment shown in FIG.

As described in detail above, according to the control device for a boiler feed water pump of the present invention, the feed water flow rate request signal and the actual feed water flow rate signal are used to adjust the deviation signal, the station load runback state signal, and the tracking signal through the calculator. The first system sends the regulator output signal to the main switch, and the output signals of the zero signal setter, increase rate setter, timer, etc. are introduced to the arithmetic unit along with the switch circuit via the switch. Then, the set value of the integrator upper limit setter is input to the upper limit value setter integrator, and its output signal and the output signal of the initial FWC signal setter at the time of station load runback are input to the main processor, and the output signal of the upper limit value setter is input to the main processor. A second system for sending the output signal to the main switching device is provided, and the main switching device selects the output signal of the main computing unit when the station load runback state signal is at the "1" level, and when it is at the "0" level. The gist of the system is that it is configured to select and output the regulator output signal, so even when the amount of water supply changes suddenly and significantly, such as when a load runback occurs in the station, it is possible to The water supply flow rate can be controlled using the turbine-driven water pump, which was previously possible, and the boiler inlet pressure does not decrease much, making it possible to perform in-house load run-bulk operation.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a water supply control system using a conventional turbine-operated feed water pump, Fig. 2 is a block diagram showing an embodiment of the boiler feed water pump control device of the present invention, and Fig. 3A is a boiler feed water pump same as above. Fig. 3B shows an example of the change in water supply flow rate obtained experimentally by simulation when the feed water control signal is given. Figure 3C shows an example of changes in boiler inlet pressure and main steam pressure obtained experimentally through simulation when a feed water control signal is given, and Figure 4 shows the invention A block diagram showing only the different parts from the second embodiment of another embodiment of the boiler feed pump control device of the present invention, and FIG. 5 is a feed diagram of the boiler feed pump control device of the present invention shown in FIG. FIG. 5 is a diagram showing changes in the water control signal and the feed water control signal of the boiler feed pump control device of the present invention shown in FIG. 4; 13, 35... Arithmetic unit, 22... Main addition/subtraction computing unit, 1
6, 32...Switcher, 14...Adjuster, 18...
Governor for operating turbine water supply pump, 21...Timer, 2
4...Initial FWC signal setter during FCB, 26...
Integrator with upper limit value setter, 28... Zero signal setter, 29
...FWC signal increase rate setter after FCB, 38...
Integrator upper limit setting device, 39... Water supply return flow rate setting device, 4
1...1st order delay element, 42...Time constant setter. Figure 1 Figure 3 Figure 2 Figure 5 Figure 4

Claims (1)

[Claims] 1. A first system that inputs the water supply flow rate request signal and the actual water supply flow rate signal to the regulator via the addition/subtraction calculator, and the deviation signal, the station load runback status signal, and the tracking signal, and sends this regulator output signal to the main switching device. system, a zero signal setter that sets the FWC signal increase rate to zero, a setter that sets the FWC signal increase rate after an in-station load runback occurs, and a timer that converts from ``0'' level to ``1'' level after set time ti. The output signal is introduced into an addition/subtraction calculator via a switch circuit that is located downstream of the timer and is equipped with a switch that opens and closes in response to the output signal of the timer, and is connected to an upper limit value setter together with the set value of an integrator upper limit setter. a second integrator that inputs its output signal and the output signal of the initial FWC signal setter at the time of in-house load runback to the main addition/subtraction calculator, and sends the output signal of the main addition/subtraction calculator to the main switching device; The main switch selects the output signal of the main addition/subtraction calculator when the station load runback status signal is at the "1" level, and selects the regulator output signal when the station load runback status signal is at the "0" level. 1. A control device for a boiler feed water pump, characterized in that it is configured to supply water instantaneously in response to the situation.