JPS607171B2 - Turbine-driven water pump control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler feed water control system, and in particular to a water feed pump that controls the boiler feed water flow rate using the rotational speed of a steam turbine, and a water feed water pump turbine control method when the boiler recirculation flow rate is simultaneously and continuously controlled. This invention relates to a control method for preventing flow rate drop trips.

FIG. 1 shows a water supply pump 4 driven by a steam turbine 5 and a control system around it, which is used in a conventional large-capacity thermal or nuclear power plant.

The water supply to the boiler 8 flows from the water supply source pipe 1, and the differential pressure generator 2
After being pressurized by a water supply pump 4 driven by a steam turbine 5, the water is supplied to a boiler 8 through a boiler water supply pipe 7.
9 to 10 are a feed water recirculation pipe and a feed water recirculation flow rate control valve, respectively.

This is installed in order to open the feed water recirculation valve, which is a bypass, when the feed water flow rate of the boiler 8 decreases and becomes less than the minimum feed water flow rate required by the water feed pump 4, and to secure the water feed flow rate of the water pump 4. ing. Note that when the minimum water supply flow rate of the water supply pump cannot be ensured, the pump cannot be continuously operated, so the steam of the steam turbine 5, which is the drive source of the water supply pump, is cut off and automatically stopped. These devices are controlled as follows. Water supply amount request signal 11 from master automatic control system
The actual flow rate signal of the feed water flow rate measuring device 3 installed on the inlet side of the pump 4 and the deviation of the feed water flow rate deviation calculator 12 are calculated, and after proportional integral operation is performed by the feed water controller 13, the turbine steam control valve 6 is
The feedwater flow rate is controlled by controlling the speed of the steam turbine, that is, the rotational speed of the feedwater pump. On the other hand, the feed water recirculation flow rate 40 is given a constant value setting (minimum flow rate Q of the pump 4) by the recirculation flow rate setting device 14, and the deviation from the actual flow rate of the feed water flow rate measuring device 3 is calculated by the recirculation flow rate deviation calculator 15. The opening of the recirculation flow rate 40 is controlled using the feed water recirculation valve 10 using the recirculation flow rate controller 16. FIG. This figure shows the transient characteristics when the water supply flow rate request signal 11 decreases toward zero.
3 works to close the turbine steam control valve 6 and reduce the feed water flow rate 30 to zero, so the rotational speed of the steam turbine 5 decreases and the discharge flow rate 30 of the water feed pump 4 decreases toward zero. At this time, the recirculation flow rate control system is activated when the minimum flow rate Qo is reached due to the decrease in the feedwater flow rate, and the recirculation flow rate controller 16 opens the feedwater recirculation valve 10. However, since the water pump 4 has no driving force and water does not flow, the water pump flow rate 3 becomes less than the water pump minimum flow limit value Qo, and eventually becomes zero after the inertia time constant of the water pump 4 and the turbine 5, and the water pump had the disadvantage of automatically shutting down due to the drop in water supply flow rate mentioned above.

It is an object of the present invention to provide a steam turbine cantering water supply system that enables the water supply pump to maintain the minimum flow rate limit value Qo and to operate continuously even when the water supply flow rate request signal rapidly decreases, without causing the water supply pump turbine to automatically stop due to the decrease in flow rate. The objective is to provide a pump control method.

2 and 3 are drawings showing the control system of the present invention, and numerals 1 to 16 indicate the same components as in FIG. 1. The difference between Fig. 2 and the conventional example shown in Fig. 1 is the recirculation flow rate controller 1.
The output signal of 6 is sent to an adder 17 as a water supply amount request signal
This is the point to be added to. The difference between the control system in FIG. 3 and the conventional example is that the control signal for the steam control valve 6 driven by the feed water pump is generated by a function generator 19 using the setting signals of the feed water controller 13 and the recirculation flow rate setting device 14. The water pump is in the 4th position.
・A high value priority circuit 18 is provided with a signal converted to a signal for maintaining the flow rate value, and this output signal is used to control the water supply pump 4.
The reason is that a lower limit value has been set for the discharge flow rate.

FIG. 5 shows the transient response characteristics of the water supply pump discharge flow rate according to the invention.

In the control system shown in FIG. 2, when the feedwater flow rate request signal 11 rapidly decreases toward zero over time, the feedwater flow rate controller 13 initially closes the evening bin steam control valve 6 to reduce the rotational speed of the turbine and reduce the water supply. Reduce pump discharge flow rate. When the feed water flow rate 11 reaches the feed water pump minimum flow limit value Qo, the recirculation flow rate deviation calculator 15 outputs the deviation on the open side of the recirculation valve, and a signal from the feed water recirculation valve of the recirculation flow rate controller 16 is output. In response to the signal, the output signal of the recirculation water amount correction adder 17, that is, the request signal of the water supply flow rate controller, is set to the water supply pump minimum flow rate limit value Qo. Therefore, even when the master automatic control system water supply amount request signal 11 becomes zero, the water supply pump can operate continuously while maintaining the minimum flow rate Qo of the water supply pump. The invention shown in Fig. 3 prevents the feed water pump speed from becoming lower than the pump minimum flow rate by providing a high value priority circuit 18 in the control signal of the steam turbine control valve 6.The limit signal of the high value priority circuit is used as a recirculation flow rate setting device. A constant signal, which is the output of No. 14, is adopted.

In this way, even if the output of the master automatic control system 11 rapidly drops to zero and the signal of the feed water controller 13 fluctuates transiently, the speed of the water pump turbine will be fixed at the minimum flow rate speed of the water pump. , it is possible to operate the water pump continuously while maintaining the minimum flow rate of the water pump. Further, its transient characteristics are similar to those shown in FIG. 5, and the same effects as the invention shown in FIG. 2 can be obtained. The key point of the present invention is that a circuit for ensuring a minimum flow rate of water supply is added to the speed control system of the water supply pump turbine.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a control system for a conventionally used steam turbine-driven water feed pump, FIGS. 2 and 3 are diagrams showing a control system for a steam turbine-driven water pump according to the present invention, and FIG. FIG. 5 is a diagram showing the transient characteristics of the water supply pump flow rate when the water supply amount request signal of the conventional steam turbine-driven water supply pump rapidly decreases, and FIG. FIG. 6 is a diagram showing the transient characteristics of the water supply pump flow rate when the water supply amount request signal of the pump rapidly decreases. 1... Water supply main pipe, 2... Differential pressure generator, 3.
...Water supply flow rate transmitter, 4...Water supply pump, 5
...Steam regulator, 6...Turbine steam control valve, 7. ．． ．． ．． ．． ．． Boiler water supply pipe, 8...
・Boiler, 9... Water supply recirculation piping, 10...
・Water supply recirculation valve, 11...Water supply amount request signal, 1
2...Water supply deviation calculator, 13...Water supply controller 14...Recirculation flow rate setting device. Figure 2 Figure 4 Figure 3 Figure 5

Claims (1)

[Claims] 1. A turbine whose rotation speed is controlled by controlling the opening degree of an artificial valve, a water supply pump driven by the turbine, and a water supply pump provided on a pipe that returns the discharge flow rate of the pump to the pump inlet side. a recirculation valve, a first adder for determining the deviation between the water supply demand and the suction flow rate of the water supply pump, and a first regulator that obtains an output according to the output of the adder and controls the opening degree of the turbine artificial valve. , a second adder for determining the deviation between the minimum feed water flow rate value allowable to the feed water pump and the suction flow rate of the water feed pump; obtaining an output according to the output of the adder and controlling the opening degree of the recirculation valve; In a control device for a turbine-driven water pump that includes a second regulator, the sum of the output of the second regulator and the water supply demand is calculated, and the turbine inlet valve is controlled according to the difference between this sum and the suction flow rate. A control device for a turbine-driven water pump, characterized in that: 2. A turbine whose rotation speed is controlled by controlling the opening of an artificial valve, a water supply pump driven by the turbine, a recirculation valve provided on a pipe for returning the discharge flow rate of the pump to the pump inlet side, and a water supply. a first adder for determining the deviation between the requested amount and the suction flow rate of the feed water pump; a first regulator for obtaining an output according to the output of the adder and controlling the opening degree of the turbine inlet valve; a second adder for determining the deviation between the minimum feedwater flow rate value and the suction flow rate of the water supply pump; a second regulator for obtaining an output according to the output of the adder and controlling the opening degree of the recirculation valve; In a control device for a turbine-driven water feed pump, an output that increases the feed water flow rate is selected from an output corresponding to a minimum feed water flow rate value allowable to the water feed pump and a first regulator output. 1. A control device for a turbine-driven water supply pump, characterized in that a selection means is added, and a turbine artificial valve is controlled by the output of the selection means.