JPH0335566B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of the Invention The present invention relates to a feed water flow rate control device for a power plant.

(b) Prior art Figure 1 shows a block diagram of a water supply system for a thermal power plant. In Figure 1, superheated steam generated in boiler 1 is led to main turbine 2, where the expanded steam is returned to boiler 1, reheated to an appropriate temperature in reheater 3, and then returned to main turbine 2. The water is guided and expanded, cooled in a condenser 4 to become saturated water, steam turbine-driven pump (T-BFP-A) 5, steam turbine-driven pump (T-BFP-B) 6, and electric motor-driven pump (M-BFP). 7 or 2
The pressure of the water is increased by these water supply pumps, and the water is fed to the boiler 1. 8 is a motor-driven pump (M-BFP)
This is a water supply control valve provided on the discharge side.

The water supply flow rate required by the boiler 1 is determined mainly from the load command, and a correction of the steam pressure at the outlet of the boiler 1 is added thereto to create the required water supply amount. Then, by driving the steam turbine drive pump (T-BFP-A) 5, the steam turbine drive pump (T-BFP-B) 6, and the water supply control valve 8 with this water supply demand as the target value, the target value is achieved. Water supply control is performed to follow the water supply flow rate.

One water supply pump is sufficient in the low load range, but generally two steam turbine-driven pumps are used to supply water between 50% rated load and 100% rated load. Switching from operating one water pump to operating two water pumps requires 50
Performed at % rated load.

At 50% rated load, one turbine-driven pump is in automatic operation and the remaining turbine-driven pump is started. Then, when the water supply is gradually increased and the water supply flow rates of the two turbine-driven pumps become equal, the turbine-driven pump that was additionally started is switched from manual to automatic, and the two water pumps are automatically operated. Become. These two water supply pumps increase the water supply flow rate according to the water supply flow rate command, making it possible to operate from 50% rated load to 100% rated load.

The conceptual diagram of the additional start-up of the second water supply pump is shown in the second figure.
As shown in the figure. In Figure 2, a T is already in automatic operation.
- This is an example in which the T-BFP-B water supply pump is additionally activated in addition to the BFP-A water supply pump. Now T-BFP-
Suppose that water pump B is started at time ta. Then, the T-BFP-B water supply pump starts supplying water and increases the water supply flow rate. On the other hand, T-BFP-A
The water supply pump reduces the water supply flow rate by the amount that the water supply flow rate of the T-BFP-B water supply pump increases, and the T-BFP-A water supply pump reduces the water supply flow rate by the amount that the water supply flow rate of the T-BFP-B water supply pump increases, and the T-BFP-A water supply pump The water supply flow rate is controlled. In this way, when the water supply flow rates of both water supply pumps become equal, that is, at time tb, T-BFP
-B water pump is switched from manual to automatic.
From now on, both water supply pumps will automatically control the water supply flow rate.

The operation of the control circuit at this time is shown in a flow diagram in FIG. In FIG. 3, the water supply control device automatically controls the water supply pump or the water supply control valve so that the total water supply flow rate follows the water supply request determined mainly from the load command of the power generation plant. At 50% rated load, a corresponding water supply request is set. The main water supply deviation 9 from the total water supply flow rate is passed through a (proportional + integral) control element 10 and a water supply master 11 is obtained. The water supply master 11 serves as a water supply flow rate command for the water supply pump during automatic operation.

Here, the T-BFP-A water pump is in automatic operation, the T-BFP-B water pump is in manual operation,
It is assumed that the M-BFP water supply pump is stopped.
At this time, only the T-BFP-A water pump is controlled by the water supply master 11.
The T-BFP-B water pump is operated manually. In the T-BFP-A water supply pump, the water supply deviation 12a between the water supply master 11 and the T-BFP-A water supply flow rate is passed to a (proportional+integral) control element 14a via a changeover switch 13a.
The output signal of the control element 14a is transferred to the changeover switch 16a.
The control target 5 (T-BFP-A water supply pump) is operated via the T-BFP-A water supply pump to control the T-BFP-A water supply flow rate. The changeover switch 13a is closed during automatic operation, and the state of the changeover switch 16a is the same as the automatic operation control element 14a.
and the controlled object 5 are connected.

Reference numeral 15a is an analog memory that provides an operation signal to the controlled object 5 during manual operation, and follows the output signal of the control element 14a during automatic operation.

On the other hand, the T-BFP-B water supply pump calculates the water supply deviation 12b between the water supply master 11 and the T-BFP-B water supply flow rate, but the changeover switch 13b
Since the BFP-B water supply pump is in manual operation and is open, the water supply deviation 12b is not passed through the control element 14b (proportional + integral). Controlled object 6 (T-
BFP-B water supply pump) is analog memory 15b
is operated via the changeover switch 16b using the value as an operation signal. The control element 14b follows the output signal of the analog memory 15b.
During manual operation, the changeover switch 13b is open, and the state of the changeover switch 16b is the analog memory 15b.
and the controlled object 6 are connected.

Next, since the M-BFP water pump 7 is stopped, the value in the analog memory 15m is changed to the changeover switch 16m.
is applied to the controlled object (water supply control valve) 8 as an operating signal, but the operating signal has no effect on the controlled object 8. and,
In this case, the (proportional+integral) control element 14m follows the output signal of the analog memory 15m. The water supply deviation 12m between the water supply master 11 and the M-BFP water supply flow rate is calculated, but since the changeover switch 13m is open, it is not passed through the control element 14m.

Now, T-BFP-A water supply flow rate is 100% and T-
It is assumed that the BFP-B water supply flow rate of 100% corresponds to the signal level of 10V of the water supply master 11. And T-BFP
-B water supply flow rate and M-BFP water supply flow rate are now 0%
Suppose that

At this time, if the water supply master 11 is 10V, the T-BFP-A water supply flow rate is 100%,
The total water supply flow rate at this time is T-BFP-A water supply flow rate 100
% only. In this state, manually increase the value in the analog memory 15b of the T-BFP-B water supply pump to reduce the water supply flow rate of the T-BFP-B water supply pump to 0%.
When the total water supply flow rate is gradually increased from
1 to reduce the T-BFP-A water supply flow rate. Since the water supply demand is constant, when the T-BFP-A water supply flow rate decreases by the amount that the T-BFP-B water supply flow rate increases, the total water supply flow rate matches the water supply demand, and the main water supply deviation 9 becomes zero and becomes stable. do. For example, when T-BFP-B water supply flow rate is 20%, T-
The BFP-A water supply flow rate is 80%, and the water supply master 11 at this time is 8V.

The timing for switching the T-BFP-B water supply pump from manual to automatic is when the T-BFP-B water supply pump water supply flow rate matches the water supply master 11 and the T-BFP-B water supply pump is switched from manual to automatic.
This is the time when the water supply deviation 12b of the BFP-B water supply pump becomes zero. In other words, both the T-BFP-A water supply pump water supply flow rate and the T-BFP-B water supply pump water supply flow rate
50%, when the water supply master 11 is 5V.

If the water supply system is switched from manual to automatic while a deviation remains in the water supply deviation 12b, the plant water supply system will be shaken, so when the deviation is reduced to zero in this way, the switch is made to automatic. This operation is called water supply balance. The conventional and common method for additionally starting a water supply pump was to manually increase the water supply flow rate until the water supply balance was reached, and then switch to automatic operation when the water supply balance was reached.

(c) Purpose of the Invention In view of the above points, the present invention has been devised to achieve water supply balance by switching from manual to automatic operation without causing any disturbance to the plant water supply system, even before water supply balance, that is, even for a water supply pump with zero water supply flow rate. The purpose is to provide a water supply control device that can be operated automatically.

(d) Structure of the Invention The present invention will be described below with reference to an embodiment shown in FIG. FIG. 4 is a drawing showing an embodiment of the present invention. One embodiment illustrated in FIG. 4 is a control object 6 (T-BFP-B water supply pump) in FIG. 3.
This is applied to a control circuit for controlling. Controlled object 5 (T-BFP-
The embodiment shown in FIG. 4 can also be applied to the control circuit for controlling the water supply pump A) and the control circuit for controlling the controlled object 8 (water supply control valve). The configuration and operation when the embodiment shown in FIG. 4 is applied to those control circuits are the same as the configuration and operation when applied to the T-BFP-B water supply pump illustrated in FIG. In Figure 4, T-
An example of application to a control circuit of a BFP-B water supply pump will be explained.

In FIG. 4, the integrator 17 is connected to the water supply deviation 12b.
The difference between the signal coming from the changeover switch 20 and the changeover switch 20 is inputted, and is applied to the feed water deviation calculating section as an integrator output signal 19 via the changeover switch 18. When the changeover switch 18 is in the opposite position to the integrator 17, the signal is 1.
9 becomes OV. The output signals of signal generators 21, 22, 23 are sent to integrator 17 via changeover switches 24, 25, 26 and changeover switch 20, respectively. The changeover switch 20 is connected to the signal generators 21, 22,
When it is in the opposite position to 23, this changeover switch 2
The signal sent from 0 to the integrator 17 becomes OV.
The above are the components added for the present invention, and in addition, the main water supply deviation 9 obtained by calculating the difference between the water supply request and the total water supply flow rate in FIG. 4 is (proportional + integral) control element 10 A part that obtains the water supply master 11 through the water supply master 11, a water supply deviation calculating part that receives the T-BFP-B water supply flow rate as input, and a water supply deviation 1
2b through the (proportional + integral) control element 14b via the changeover switch 13b and the output signal of the analog memory 15b are selected by the changeover switch 16b, and the control target 6 is controlled by the selected signal. The operating part is the same as that explained in FIG.

Next, the operation of such a configuration will be explained.
In FIG. 4, it is assumed that the total water supply flow rate is equal to 100% of the T-BFP-A water supply flow rate and is stable in this state. T-BFP-B water supply flow rate is now 0%
Suppose that At this time, the signal sent from the changeover switch 20 to the integrator 17 is OV (0%),
The difference between this 0% signal and the water supply deviation 12b is the integrator 1
7 input. The output signal of the integrator 17 becomes a signal 19 via a changeover switch 18 and becomes an input to the water supply deviation calculation section. The integrator 17 becomes stable as the water supply deviation 12b becomes zero. Since T-BFP-B water supply flow rate is 0%, integrator output 19 is water supply master 1
Matches 1.

Next, one of the output signals of the signal generators 21, 22, and 23 is to be used to give it to the integrator 17 via the changeover switch 20. was established for the following reasons. A turbine-driven feedwater pump increases its feedwater flow rate by increasing its rotational speed, but the relationship between the rotational speed and the feedwater flow rate changes depending on the magnitude of the boiler feedwater pressure. Naturally, at low rotation speeds, it is not possible to overcome the high boiler water supply pressure and supply water. In addition, a characteristic of the water supply pump is that in a low flow rate region, the water supply flow rate changes greatly in response to a minute change in rotational speed. For the above reasons, three signal generators are provided.For convenience, the signal generator 21 gives a signal setting value before the start of water supply, the signal generator 22 gives a signal setting value near the water supply start point, and the signal generator 21 gives a signal setting value near the water supply starting point. 23 is distinguished as providing a signal setting value after the start of water supply.

Assume that the T-BFP-B water supply pump is running at a low rotation speed and cannot push the water into the boiler, and the water supply flow rate is 0%. In this state, T-BFP
- It is checked whether the B water supply pump discharge pressure is within a predetermined pressure difference from the boiler feed water pressure, and if the difference is lower than the predetermined pressure difference, the changeover switch 24 is automatically closed on that condition. That is, the signal setting value of the signal generator 21 is selected. When a request for switching the T-BFP-B water supply pump from manual to automatic is sent as a command from outside the water supply control device, the changeover switch 20 automatically switches the signal generator 21 on condition of the switching request to automatic. This signal setting value is given as an input to the integrator 17. At the same time, the changeover switch 13b is closed, the changeover switch 16b is switched to the control element 14b side, so that the output of the control element 14b is connected to the controlled object 6, and the T-BFP-B water supply pump is put into automatic operation mode. .

In this state, the water supply deviation 12b is controlled by the (proportional + integral) control element 14 via the closed changeover switch 13b.
b, and the output signal of the control element 14b is sent as an operation signal to the controlled object 6 via the changeover switch 16b. If the signal setting value of the signal generator 21 is set to 2% for convenience, the integrator 17 becomes stable when the water supply deviation 12b reaches 2%. At this time, the output signal 19 of the integrator 17 is 98% and the water supply master 11 is 100%. The (proportional+integral) control element 14b inputs the 2% water supply deviation 12b, calculates an operation signal, and operates the controlled object 6. The operation signal is the control element 14
It continues to increase at a constant rate of increase determined by the integral element of b.

In this way, as the T-BFP-B water supply pump rotation speed increases and approaches the vicinity of the water supply start point where water can be supplied, the pressure difference between the T-BFP-B water supply pump discharge pressure and the boiler water supply pressure becomes a predetermined pressure difference. The changeover switch 24 is automatically opened and the changeover switch 25 is closed on the condition that it is within the range of . If the signal setting value of the signal generator 22 is 0.5%, the integrator 17 becomes stable when the water supply deviation 12b reaches 0.5%. At this point, the T-BFP-B water supply flow rate is still 0%, so the output signal of the integrator 17 is 99.5% and the water supply master 11 is 100%. Near the start of water supply, the increase rate of the operation signal is made small to compensate for the high gain at the start of water supply, that is, in the low flow rate range of the water supply pump.

In this way, when the water supply start point is reached and the water supply begins to flow, the T-BFP-B water supply flow rate begins to increase from 0%. When the T-BFP-B water supply flow rate reaches 10%, the T-BFP-A water supply flow rate reaches 90%.
So the water supply master 11 is set to 9V. The output signal 19 of the integrator 17 is 79.5%, maintaining the water supply deviation 12b at 0.5%. After passing near this water supply starting point, next T-BFP-
Under the condition that the discharge pressure of the B water feed pump is higher than the boiler feed water pressure by a predetermined pressure difference or more, the changeover switch 25 is automatically opened and the changeover switch 26 is opened.
is closed and the signal generator signal setting value and water supply deviation 12
The difference in b is given as an input to the integrator 17. If the signal setting value of the signal generator 23 is 1%, when the water supply deviation 12b reaches 1%, the integrator 17
becomes stable. The operation signal is the control element 1
It continues to increase at a constant rate of increase determined by the integral element of 4b. Then, when the T-BFP-B water supply flow rate reaches 50%, the T-BFP-A water supply flow rate is 50%, and the water supply master 11 is 5V. At this time, integrator 17
The output signal 19 of is -1%. and T-
The BFP-B water supply flow rate matches the water supply master 11.
At this point, it is assumed that the additional start-up of the T-BFP-B water pump has been completed, and the changeover switch 18 automatically switches between the integrator 17 and is the opposite side, i.e.
Switches to OV side. Since the signal 19 becomes OV, that is, 0%, the control circuit returns to the same one as in the example shown in FIG. 3, and automatic operation continues.

In Fig. 4, an example of additional activation of the T-BFP-B water supply pump has been explained, but the T-BFP-A water supply pump and the M-BFP water supply pump are also
This can be achieved by adding a circuit similar to that of the BFP-B water pump.

(e) Effects of the Invention Since the present invention is configured as described above, even if the water supply pump has a zero water supply flow rate, it can be switched from manual to automatic mode without causing any disturbance to the plant water supply system, and water can be supplied from an increase in the water supply flow rate. Water supply control up to balance can be performed automatically.

[Brief explanation of the drawing]

Fig. 1 is a water supply system diagram of a thermal power plant to which the present invention is applied, Fig. 2 is a conceptual diagram of additional activation of a water supply pump, and Fig. 3 is a flow diagram of water supply flow rate control.
FIG. 4 is a water supply flow rate control flow diagram showing one embodiment of the present invention. 1...Boiler, 2...Main turbine, 3...Reheater, 4...Condenser, 5...Steam turbine driven pump T-BFP-A, 6...Steam turbine driven pump T-BFP-B , 7...Electric motor driven pump M-
BFP, 8... Water supply control valve, 9... Main water supply deviation,
10... (proportional + integral) control element, 11... water supply master, 12... water supply deviation, 13... changeover switch, 14... (proportional + integral) control element, 15...
Analog memory, 16...Switch switch, 17...
... Integrator, 18... Changeover switch, 19... Water supply deviation calculation section input, 20... Changeover switch, 21,
22, 23...signal generator, 24, 25, 26...
...Switch.

Claims (1)

[Claims] 1. In a water supply control device that calculates the water supply command deviation between the water supply flow rate and its water supply command, and controls the controlled object using the operation signal obtained by passing the water supply deviation through a control element, a system that responds to gain changes in the water supply pump water flow rate is used. a plurality of signal generators for respectively giving a target value of the water supply deviation determined in advance; a changeover switch that switches each of the signal generators correspondingly; an integral element that inputs the difference between the target value set for the signal generator in use and the water supply deviation; 1. A water supply control device, comprising: a control element for controlling the integral element so as to maintain the water supply balance, and detecting completion of water supply balance when the value of the integral element reaches a predetermined value.