JPH059682B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water supply pump control device, and particularly to a water supply pump control device that controls a plurality of water supply pumps that supply water to a steam generator in a power generation plant or the like based on a predetermined operation command. Regarding.

The water supply pumps used to supply water to the steam generators of power plants usually consist of an electric motor-driven water pump and two turbine-driven water pumps with variable rotation speeds installed in parallel. Water is passed to the steam generator using a drive water pump. After that, the turbine-driven water pump is started, but water is not immediately passed to the steam generator, and the water from the turbine-driven water pump is circulated to its inlet side to perform so-called recirculation operation, and recirculation is started at an appropriate point. Stop and water flow to the steam generator. Note that the motor-powered water supply pump is then stopped. The conventional startup method for turbine-driven water pumps is to set a predetermined target turbine rotation speed and increase the rotation speed to this rotation speed, and this method is almost satisfactory in conventional constant-pressure power generation plants. However, it was found that the transition to turbine-driven water pumps could not be made smoothly in variable-voltage power plants.

This can be explained using the characteristic diagram shown in Figure 1, which shows the relationship between the discharge pressure H and flow rate Q of the water supply system. In the figure, the horizontal axis is the water supply flow rate, the vertical axis is the pump discharge pressure, and the pump rotation speed N ₁ , N ₂ , N ₃ and the system head characteristics h _S , h _T of the power plant, the discharge pressure H
and the flow rate Q is determined. Among these, the system head characteristic h _S is for a constant pressure operation power plant, and the pump discharge pressure H is a nearly constant value over the entire feed water flow rate, so the target turbine rotation speed when starting the turbine feed water pump is It wasn't that difficult to set up. In other words, the discharge pressure determined by the system head (the pressure at the outlet header of the parallel pump group) is
H ₁ , the turbine-driven water pump outlet pressure determined by the predetermined turbine rotational speed target value for starting the turbine-driven water pump at a certain point in time is
H ₂ , this pressure difference when water starts to be supplied from the turbine-driven feedwater pump to the water supply pump discharge side confluence point is small no matter where the water supply starts, so the setting of the turbine rotation speed target value is almost unambiguous. It would have been a good idea to make a decision.

However, in a variable voltage power generation plant, the system head characteristic h _T varies greatly depending on changes in the feed water flow rate (plant load), so the discharge pressure H ₁ determined at the system head and the turbine-driven feed water pump starting at a certain point in time are predetermined. The difference in the turbine-driven water supply pump outlet pressure H ₂ determined by the turbine rotational speed target value will inevitably become large, and if this continues, a situation will arise in which water cannot be supplied forever when water starts flowing from the turbine-driven water supply pump.
In other words, since the conditions for starting water flow from the turbine-driven water supply pump are not uniformly determined, the discharge pressure determined by the system head at the time water flow starts is not determined, so it is necessary to set the target turbine rotation speed value to a constant value in advance. I can't. This problem needs to be solved not only for the first turbine-driven water pump, but also for the second turbine-driven water pump.

FIG. 1 is a characteristic diagram showing the relationship between the flow rate Q and the discharge pressure H of the water supply system, with the horizontal axis representing the flow rate Q and the vertical axis representing the discharge pressure H. In the figure, N ₁ , N ₂ and N ₃ represent the rotational speed of the water pump, h _S represents the system head characteristic of a constant pressure operating plant, and h _T represents the system head characteristic of a variable pressure operating plant. In the case of a constant-pressure operation plant, as shown in the figure, the system head curve h _S is flat, so the change in discharge pressure due to changes in the rotation speed of the turbine-driven water pump is small, and the Even if the numerical target value is set to a constant value, the influence of the above drawback is small. However, in the case of a variable pressure plant, the main steam pressure changes depending on the load, so the system head h _T of the water supply system changes more than the system head h _S of a constant pressure plant. Therefore, especially in the case of a variable pressure plant, the rotational speed corresponding to the water supply start point of the turbine-driven water supply pump is not uniformly determined, and it is not preferable to set the rotational speed target value to a constant value. For this reason, there was a drawback that it was difficult to control the water pump.

The purpose of the present invention is to solve the above-mentioned drawbacks of the prior art and add a water supply pump that can perform stable and smooth water supply control regardless of changes in the system head of the water supply system when water is being supplied to a steam generator by the water supply pump. An object of the present invention is to provide a water supply pump control device when starting up.

In order to achieve the above object, the present invention obtains the rotation speed corresponding to the water supply start point of the water supply pump based on the differential pressure between the discharge pressure of the turbine-driven water supply pump and the pressure at the water supply pump discharge side confluence point, and The number of rotations of the water supply pump that is additionally activated is controlled accordingly.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 2 is a system diagram showing a schematic configuration of a power generation plant to which the feedwater pump control device according to the present invention is applied. In the figure, a boiler 10 as a steam generator includes a turbine-driven water supply pump 12 and a
4 and a water supply 10 from an electric motor-driven water supply pump 16
The boiler 10 is supplied with fuel from a fuel pump (not shown) and air from a fan. This boiler 10 converts feed water 100 into steam 102 in accordance with the combustion of the fuel, and supplies this to a turbine 20 via a control valve 18 for the steam 102. This turbine 20
is configured to generate rotational work according to the steam 102A controlled by the control valve 18, and is configured to be able to transmit the rotational work to the generator 22. This generator 20 is configured to be able to generate electric power according to its work.
Further, the turbine 20 is configured to send most of its steam 102A to a double water machine 24,
The double water machine 24 is adapted to return the steam 102A to the pumps 12, 14 and 16 as double water 104. The suction sides of the water supply pumps 12, 14, and 16 are shared, and their discharge sides are connected through check valves 26, 30, and 34, and stop valves 28, 32, and 36, which are connected in series, respectively, as shown in the figure. The water is commonly connected to the confluence point and is supplied to the boiler 10 as feed water 100. Furthermore, the turbine-driven water pumps 12 and 14 are
By controlling the bleed air 106 from the turbine 20 with respective control valves 38 and 40, the turbines 42 and 44 are driven to rotate. These water supply pumps 12 and 14 are provided with rotation detectors 46 and 48 that detect the number of rotations thereof. Note that 50 is an electric motor. moreover,
52 and 54 are pressure detectors provided on the discharge sides of the turbine-driven water supply pumps 12 and 14;
is a pressure detector provided at a portion after the discharge side confluence of the water supply pumps 12, 14, and 16. Further, the water supply pipe is provided with a flow rate detector 58 that detects the flow rate of the water supply 100, and the steam pipe is further provided with a flow rate detector 6 that detects the flow rate and pressure of the steam 102.
0 and a pressure detector 62 are provided. In addition, a detector 64 is provided at the output of the generator 22 to detect the amount of power generated.

The control circuit 66 that controls the power generation plant is
Various power generation commands 68 and various detectors 46, 48,
Detection signals from 52, 54, 56, 58, 60, 62, and 64 are taken in, and based on these, the control valve 18 and regulating valves 38 and 40 are controlled to control the amount of generated power. ing.

In the power generation plant configured as described above, the control circuit 66 controls the combustion of the boiler 10 based on various commands 68, and controls the control valve 18 to control the rotation of the turbine 20, so that the generator 22 generates power. Control quantity. At this time, the control circuit 66 controls the various detectors 52, 54, 5 based on various commands 68.
The control valve 18, the control valves 38 and 40, and other operating parts are controlled by the detection signals from the control valves 6, 58, 60, 62, and 64.

FIG. 3 shows a specific example of the configuration of a water supply pump control device applied to a power generation plant as described above. In this figure, since the part of the embodiment shown in FIG. 2 is shown in an enlarged manner, the same reference numerals are given, and explanation of the structure thereof will be omitted, and only a brief explanation of the reference numerals will be given. 12 and 14 are turbine-driven water pumps, which are driven by steam turbines 42 and 44. Further, 16 is an electric motor-driven water supply pump, which is driven by an electric motor 50. 26,30
and 28, 32 are check valves and stop valves for the turbine-driven water pumps 12 and 14, respectively;
and 36 are a check valve and a stop valve for the motor-driven water supply pump 16. When starting up the plant, water is supplied to the boiler by the motor-driven water pump 16, and after reaching the specified load, the turbine-driven water pump 12 is started, and the water supply load is transferred to the turbine-driven water pump 12 or 1.
4 side, and a second turbine-driven water supply pump 14 is added, but when starting the turbine-driven water supply pump 12 or 14, as described above, the speed is increased to the rotation speed equivalent to the water supply starting point, It is desirable to circulate the water supply flow rate of the turbine-driven water pump to its inlet side via a recirculation system (not shown) and keep it on standby, so that a smooth transition to water supply control can be achieved. And 52, 54 and 56
is a pressure detector for executing this, and the detection signals from the pressure detectors 52, 54, and 56 are taken into the control circuit 66 to perform the above control.

FIG. 4 is a block diagram showing this embodiment of the control circuit 66. In FIG. 4, a detection signal 70 from the pressure detector 52 and a detection signal 72 from the pressure sensor 56 are input into a subtracter 74, and the subtracter 74 is configured to output a differential pressure signal (ΔP) 76. has been done. This differential pressure signal 76 is subtracted by the subtractor 7
At the same time, a signal from the target differential pressure command 68A is similarly input into a subtracter 78, and this subtracter 78 outputs a differential pressure deviation 80. This differential pressure deviation 80 is taken into a proportional-integral calculator 82, and this calculator 82 outputs a rotation speed setting value 80.
is beginning to form. The rotation speed detector 4
The actual rotational speed signal 86 from 6 is taken into a subtracter 88 together with the rotational speed setting value 84;
A rotational speed deviation of 90 is formed.
This rotational speed deviation 90 is supplied to a low value selector 94 via a proportional calculator 92.
and takes in the signal from the acceleration rate setting 68B,
Either one of the lower values is output and the proportional-integral calculator 96
It is now possible to supply This proportional-integral calculator 96 is adapted to control the control valve 38 of the turbine 42.

The operation of the control circuit configured as described above will be explained next.

In FIG. 4, a signal 90 is an actual rotational speed signal 86 detected by a rotational speed detector 46 that detects the rotational speed of the turbine-driven water supply pump 12 and a rotational speed setting value 84.
is the deviation calculated by the subtractor 88, and the control valve 38 of the driving turbine 42, which is the operating end, is controlled by the deviation signal 90 via the proportional calculator 92 and the proportional integral calculator 96, Increase the speed to the set rotation speed. Furthermore, the purpose of the rotational speed change rate setter 68B and the low value selector 94 is to limit the rate of change when the deviation between the actual rotational speed and the target rotational speed at the initial stage of speed increase is large. This embodiment is characterized in that the rotation speed setting value 84 is variable as described above. In addition, as explained in FIG. )76
By calculating the deviation 80 between this and the signal of the signal generator 68A which has set 0 as the target differential pressure, for example, through the proportional-integral calculator 82, it is possible to obtain the rotation speed setting value 84 at which the differential pressure becomes 0. can.

According to this embodiment, the water supply pump 12 or 14
water supply pressure (signal detected by pressure detector 52) and water supply pressure at the discharge side confluence section (signal detected by pressure detector 52).
It is possible to automatically increase the speed of the turbine-driven water supply pump 12 to the rotation speed (84) at which the differential pressure (signal detected at step 6) becomes 0, that is, the rotation speed corresponding to the water supply start point. Note that the water supply pump 14 is also configured with a control circuit in the same manner.

According to this embodiment, the rotational speed of the water supply pump 12 or 14 can be increased to the level equivalent to the water supply starting point regardless of changes in the system head of the water supply system, and the advantage is that the subsequent transition to water supply control is smooth. be.

As described above, according to the present invention, the water supply control of the water supply pump that is additionally activated can be made stable and smooth regardless of changes in the system head of the water supply system.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram showing the relationship between the discharge pressure and flow rate of the water supply system, Fig. 2 is a system diagram showing the schematic configuration of a power generation plant to which an embodiment of the present invention is applied, and Fig. 3 is a diagram showing the schematic configuration of a power plant to which an embodiment of the present invention is applied. FIG. 4 is a block diagram showing the configuration of a control circuit according to an embodiment of the present invention. 12, 14...Turbine-driven water pump, 16...
Electric motor-powered water supply pump, 38, 40...Adjustment valve, 4
2, 44...Turbine, 52, 54...Pressure detector,
56... Pressure detector at confluence section, 66... Control circuit, 6
8...Command, 74,78,88...Subtractor, 82,9
6...Proportional integral calculator, 94...Low value selector.

Claims (1)

[Claims] 1. Applicable to a plant in which water from a plurality of water pumps connected in parallel is supplied to a steam generator via a discharge confluence section, where at least one water pump supplies water to the steam generator. A water supply pump control device for additionally starting other water supply pumps when the water supply pump is running, including a water supply pump whose rotation speed can be controlled, a plurality of water supply pumps connected in parallel, and a water supply pump whose rotation speed can be controlled. a check valve provided between a discharge portion and a discharge merging portion of the plurality of water supply pumps; a first pressure detector provided at the discharge merging portion of the plurality of water supply pumps; and a first pressure detector provided at the discharge merging portion of the plurality of water supply pumps; a second pressure detector provided between the discharge part and the check valve;
a first subtractor for calculating a pressure difference between detection signals of the first and second pressure detectors; and an output of the first subtractor;
a second subtractor for calculating a difference between a target value of a pressure difference for preventing the discharge pressure of the water supply pump whose rotation speed can be controlled from becoming higher than the pressure at the discharge confluence section and from starting water supply; a rotation speed target value calculation circuit that determines a rotation speed target value of the water supply pump whose rotation speed can be controlled according to the output of the subtractor; and a rotation speed target value calculation circuit that controls the rotation speed of the water supply pump according to the output of the rotation speed target value calculation circuit. A water supply pump control device comprising: a control circuit for controlling a water supply pump;