JPH0333495A - Control device for condensate pump - Google Patents

Abstract

PURPOSE:To perform stable control of water supply by controlling the revolving speed of a condensate pump according to the deviation of the revolving speed signal, which is determined from the sensed water supply pump suction pressure on the water supply system, from the set value signal, and thereby holding the suction pressure of a water suction pump constant. CONSTITUTION:The pressure of condensate from a water condenser 1 is boosted by a condensate pump 2, and the condensate is supplied to a nuclear reactor 5 through a motor-driven pump 3 at the time of low load and through a turbine pump 4 at the time of high load, and there the condensate is heated to become a high pressure vapor to drive a turbine. The suction pressures of pumps 3, 4 are sensed 13 and fed to a revolving speed calculating device 14 as a pressure signal, and there the revolving speed is computed and fed to a revolving speed control device 15 as a revolving speed signal. This revolving speed control device 15 determines the control deviation between the given revolving speed signal and the predetermined set value signal, and the result from computation is given to the motor 16 of the condensate pump 2 as a revolving speed command signal. This holds the suction pressure of the water supply pump 2 constant, and water supply control is carried out stably.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention makes it possible to maintain the rotation speed of a condensate pump at a desired value when the feed water pump suction pressure in a turbine plant fluctuates, for example. This invention relates to a condensate pump control device.

(Prior art) The system from the condenser of a turbine plant to the reactor consists of two areas, the so-called condensate system and the feed water system, and each area is equipped with condensate and feed water pumps that flow condensate and feed water. It will be done. FIG. 3 shows an example of the arrangement of such condensate and water supply pumps.

Condensate extracted from the condenser 1 is pressurized by the condensate pump 2 and sent to the water supply system. During this time, the condensate is heated as it passes through a group of feedwater heaters (not shown). After this, the feed water led to the feed water pump 3.4 of the water supply system is supplied to the reactor 5 and heated, and is used as working steam for the plant by the turbine (
(not shown). Note that the water supply system is also equipped with a group of feed water heaters, and the water supply is heated by heated steam.

Further, the water supply pump 3.4 is classified into an electric motor-driven water pump 3 and a turbine-driven water pump 4 depending on the power used. Both are used as an electric motor-driven water pump 3 while handling low loads such as when starting and stopping the plant.
is used, and after a certain load is exceeded, the water supply pump 4 that utilizes the power of the drive turbine 6 is used.

On the other hand, in order to control the water level in the nuclear reactor 5, the water supply flow rate is adjusted in the water supply system. For example, at the time of starting/stopping, etc., the water supply control valve 8
During normal operation when the plant load is stable, the feed water flow rate is adjusted by controlling the rotation speed of the drive turbine 6.

Furthermore, when the required flow rate on the reactor 5 side decreases and falls below the minimum flow rate required to avoid heat generation in the feed water pump 4, the feed water pump 4 is configured to release excess feed water from the water supply system.
A branch pipe 9 branched from the discharge side of the condenser 1 connects the other end to the condenser 1.
It is connected to the A minimum flow control valve 10 is interposed in the path of this branch pipe 9, and a minimum flow control device 1 is installed.
The opening degree is adjusted based on a control signal output from 1. Note that the reference numeral 12 indicates a flow rate detector.

(Problems to be Solved by the Invention) As described above, the supply of water at the time of plant start-up begins with the water supply pump 3 driven by the electric motor, and is then switched to the water supply pump 4 that utilizes the power of the drive turbine 6. In order to smoothly switch to the water supply pump 4 and to prevent large fluctuations in the water supply flow rate, first open the minimum flow rate control valve 10 to a constant opening so that the flow rate of the water supply pump 4 is maintained. When the flow rate increases to this value, the minimum flow rate control valve 10 is closed. Therefore, the suction flow rate of the water supply pump 4 is taken out as a flow rate signal by the flow rate detector 12, which is compared with a set value signal, and when the suction flow rate exceeds the set flow rate, the opening degree of the minimum flow rate control valve 10 is closed. I am trying to make it work. As a result of this operation, the water supply flow rate begins to increase, but the water supply control device 7 throttles the water supply control valve 8 provided on the discharge side of the water supply pump 3 operated in parallel, so that the total flow rate is kept constant.

During this time, in the condensate system, the condensate flow rate fluctuates by an amount commensurate with the decrease in the opening degree of the minimum flow rate control valve 10. At this time,
Since the double water pump 2 has the characteristics as shown in FIG. 4, the discharge pressure increases.

That is, when the rotational speed is n, when the flow rate decreases from Ql to Q2, the pressure head changes from H to H2 by 1, and the pump discharge pressure increases. As a result, the suction pressure of the water supply pump 4 increases, and the water supply flow rate further increases. Due to this increase in flow rate, the minimum flow rate control valve 10 is narrowed down from its previous opening degree, and this repetition may cause the minimum flow rate control valve 10 to close suddenly. These minimal flows 11! Unstable operation of the Jim valve 10 is undesirable because it impairs the stability of water supply control.

In addition, a minimum rotation speed is determined for the drive turbine 6 in order to avoid operation in a dangerous speed range that induces excessive vibration of the drive turbine 6, and the drive turbine 6 is set at a certain high rotation speed in order to further improve controllability. Although it is desirable to operate in several regions, in regions where the flow rate is low, the head required for the water supply pump 4 becomes even smaller, so that it is forced to operate at a low rotation speed.

An object of the present invention is to provide a condensate pump control device that eliminates unstable operation of a minimum flow control valve and stabilizes water supply control.

Another object is to provide a condensate pump control system that maintains the speed of the feedwater pump drive turbine at a relatively high level.

[Structure of the Invention] (Means for Solving the Problems) A condensate pump control device according to the present invention includes a condensate pump that boosts the pressure of condensate extracted from a condenser and sends it to a water supply system, and The present invention is characterized by comprising a device that outputs a rotation speed command signal to the drive unit of the condensate pump in accordance with a deviation between a rotation speed signal and a set value signal from which the water supply pump suction pressure of the water supply system is determined.

(Function) FIG. 2 is a pressure head-flow characteristic diagram when the rotation speed of the condensate pump can be set arbitrarily. Condensate pump rotation speed n
Point A is the operating point when the flow rate Ql is maintained at .

Here, the flow rate of the condensate pump fluctuates from the flow rate Q to the flow f
When changing to ilQ2, if the rotation speed remains n2, the operating point moves to point B, and at this time, the positive force head moves to H corresponding to point A.
, becomes H2 corresponding to point B (same state as in Fig. 4), but if the rotation speed is controlled to 02, which is lower than 01, the operating point moves to point C, and the pressure head Hl
can be kept at the same level.

In other words, a rotation speed signal obtained from the water supply pump suction pressure to keep the water supply pump suction pressure of the water supply system constant;
The rotation speed of the condensate pump is controlled according to the deviation from a predetermined set value signal.

(Example) An embodiment of the present invention will be described below with reference to FIG.

In the configuration shown in FIG. 1, the same components as those shown in FIG. 3 described above are given the same reference numerals, and the explanation thereof will be omitted.

In FIG. 1, the suction pressure of the water supply pump 3.4 is detected by a pressure detector 13 and inputted to a rotation speed calculation device 14 as a pressure signal. The rotational speed calculation device 14 calculates the rotational speed based on the pressure signal, and inputs it to the rotational speed control device 15 as a rotational speed signal. The rotation speed control device 15 calculates a control deviation between the given rotation speed signal and a predetermined set value signal, and outputs the calculation result to the electric motor 16 of the condensate pump 2 as a rotation speed command signal. .

Next, the effect of the above configuration will be explained.

The suction pressure of the water supply pump 3.4 detected by the pressure detector 13 is inputted as a pressure signal to the rotation speed calculation device 14, where the following calculation is executed and converted into a rotation speed signal. That is, the distance between the pressure head H and the rotational speed n is H" n 2
There is a relationship, and the number of rotations can be found for a given suction pressure. This rotational speed signal is input to the rotational speed control device 15 which calculates the deviation, the deviation is determined by comparison with the rotational speed setting value signal, and the calculation result is used as the rotational speed command to control the rotational speed of the electric motor 16 of the condensate pump 2. taken out as a signal.

This new rotation speed command signal is transmitted to the electric motor 16 of the condensate pump 2.
The number of revolutions is increased or decreased from the previous number of revolutions depending on the positive or negative values.

For example, when the opening degree of the minimum flow rate control valve 10 is kept constant at plant startup, if the condensate flow rate changes in an increasing direction, the pressure signal given to the rotation speed calculation device 14 will be at a high level. Then, the rotation speed signal output from the rotation speed calculation device 14 changes, and the deviation determined by the rotation speed control device 15 increases, and the rotation speed command signal becomes a value commensurate with the new rotation speed, which is lower than before. be changed.

As a result, the suction pressure of the water supply pump 4 is reduced, and the discharge flow rate of the water supply pump 4 is kept constant. Therefore, the opening degree of the minimum flow rate control valve 10 does not change significantly before and after fluctuations in the condensate flow rate. Furthermore, even when the condensate flow rate fluctuates, the pump pressure head can be kept constant because the rotational speed changes (see Figure 2). Therefore, the suction pressure of the water supply pump 4 does not increase even in the low flow rate range, and the drive turbine 6
The rotation speed will not become too low.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and a method of detecting the condensate flow rate and calculating the rotation speed in accordance with this flow rate signal to maintain the suction pressure of the water supply pump 4 constant is possible.

[Effects of the Invention] As explained above, the present invention controls the rotation speed of the condensate pump according to the deviation between the rotation speed signal obtained from the detected suction pressure of the water supply pump in the water supply system and the set value signal. With this configuration, the suction pressure of the water supply pump can be kept constant, and the stability of water supply control can be improved.

It is also possible to maintain the speed of the drive turbine at a high level.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the condensate pump control device according to the present invention, Fig. 2 is a pressure head-flow characteristic diagram of the condensate pump according to the present invention, and Fig. 3 is a conventional condensate system and water supply system. Fig. 4 is a pressure head-flow characteristic diagram of a condensate pump according to the prior art. 2... Condensate pump 3.4... Water supply pump 10... Minimum flow control valve 13...
...Pressure detector 14...Rotation speed calculation device 15...
...Rotation speed control device 16...Motor source 2 Diagram

Claims (1)

[Claims] The difference between the condensate pump that boosts the pressure of condensate extracted from the condenser and sends it to the water supply system, the rotation speed signal obtained from the detected suction pressure of the water supply pump in the water supply system, and the set value signal. A condensate pump control device comprising: a device for outputting a rotation speed command signal to a driving section of the condensate pump in response to the rotation speed command signal.