JPS60200004A - Method of controlling feed pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a control system for a water supply pump, and in particular, a water supply pump control system suitable for controlling operation outside the hazardous area of the water supply pump itself. Regarding the method.

[Background of the invention]

The conventional control method for charging plants is a constant pressure operation control method, which controls the pressure while keeping it constant regardless of load fluctuations. However, recently, intermediate load operation has been adopted in which daily startup and shutdown are performed according to load demand, and a variable voltage operation control method has been used as the control method. This operation method is an operation method that changes the main steam pressure according to the load.

For such a system, if the conventional water pump control method is adopted as is and the load is lowered, the header pressure of the water pump will also be controlled to be lower, so the discharge pressure of the water pump will decrease. Furthermore, due to the pressure-flow characteristics of the water supply pump itself, the rotational speed of the water supply pump decreases, and the flow rate also decreases.

Pumps must always maintain a certain flow rate to protect the pump body. This flow rate is ensured by providing a recirculation line that returns from the pump outlet to the pump inlet. If the decrease in rotational speed due to a drop in header pressure and the decrease in flow rate exceed the permissible control value for this flow rate, a flashing phenomenon will occur near the outlet of the pump, causing an unbalanced flow in the pump and vibration in the direction of the pump, potentially damaging the pump's thrust bearing.

[Purpose of the invention]

The purpose of the present invention is to prevent the water supply flow rate from changing below the flow rate limit value, which causes the above-mentioned problems, that is, to prevent the water supply pump itself from entering the dangerous area when operating the water supply pump. , the pump flow rate of the pump in question -
Detects the pump discharge pressure, flow rate, and rotation speed based on the pump recirculation flow rate limit value based on the pump discharge pressure characteristics,
The purpose is to provide a suitable water pump control system by making the final water supply command for the water supply pump equal to the final water supply command by performing calculation and control.

[Summary of the invention]

The present invention provides a means for preventing the flow rate of the feed water pump from becoming lower than the limit value of the recirculation flow rate even when the feed water pump discharge pressure decreases due to a plant adopting a variable pressure operation control method. A correction signal for the water supply flow rate based on the relationship between It was designed to obtain instructions.

[Embodiments of the invention]

Figure 1 shows the characteristic curve of the water pump. This characteristic curve is usually called a QH curve.

In the figure, Ll is the pump rotation speed, L2 is the system curve, and L3
is the recirculation limit curve. The pump is operated so that the flow rate does not fall within the shaded area of the recirculation flow rate limit curve L3. This shaded area corresponds to the dangerous area.

FIG. 2 is a diagram showing an embodiment of the present invention based on the above characteristics. The flow rate to the water supply pump P is controlled by a water supply pump flow control valve FV. Further, the water supply pump P is provided with a recirculation line, and a recirculation flow rate control valve RV is provided in this path. The water supply pump P is provided with a pump rotation speed detector SX, and on the discharge side, a pump discharge pressure detector px and a water supply flow rate detector FX.

The control unit 100 controls the flow rate regulating valve FV,
This is the main part of this embodiment. This control unit 100 includes the pump discharge pressure detector PX, the water supply flow rate detector FX,
Each detected amount of pump rotation speed SX is input. moreover,
FIG. 3 shows the specific configuration of this control section 100, which also receives commands from load demands.

In FIG. 3, the command to the feedwater pump from the load demand generated from the negative pressure, main steam flow rate, and main steam temperature becomes a command 100a to the constant pressure operation pump. It should be noted that setting device No. 2 is used to set a value νA that becomes the pump command during manual operation, and switching between manual and automatic mode is performed by switch 3. That is, when the switch 3 is switched to the PI calculator 1 side, automatic operation is performed, and when the switch 3 is switched to the setting device 2 side, the operation is manual.

In this embodiment, a pump discharge pressure detector p is added to the above control system.
A control system is added that processes inputs x, water supply flow rate detector FX, and pump rotation speed detector SX.

The flow rate detector FX passes through the PI calculator 4 and then the addition/subtraction calculator 5.
In this step, the command from the load demand is corrected by the flow rate. A signal from the pump discharge pressure detector PX is input to a function generator 11. The function generator 11 sets the flow rate according to the characteristic curve shown in FIG. 1 based on the detected discharge pressure. This flow rate setting is set to a value somewhat larger than the limit value of the recirculation flow rate relative to the feed pump discharge pressure in FIG.

The addition/subtraction calculator 12 calculates the deviation between the set flow rate set corresponding to this detected discharge pressure and the detected flow rate detected by the flow rate detector FX. This deviation is calculated by the PI calculator 1
3 and is guided to a high value selector 6. This high value selector 6 also inputs the water supply command obtained from the switch 3, compares the surface input value by 1, and outputs the larger value of human power.
This becomes a water supply directive. Further, the rotational speed signal detected by the pump rotational speed detector SX is manually inputted to the function generator 21.

The function generator 21 sets the flow rate for the rotation speed based on the characteristic curve shown in FIG. 1 based on the rotation speed.

This signal is supplied to the addition/subtraction calculator 7, further corrects the water supply command, and becomes the final command 100a to the water supply pump.

The operation based on the second configuration will be explained below.

Currently, while operating at a certain load, the water supply flow on the claw side remains constant. However, let us consider a case where the water supply flow rate starts to be reduced due to some reason in response to a command signal from the load demand.

By adding the water supply meteor signal to the load demand in the adder/subtractor 5, a water supply command is outputted so as to quickly approach the required water supply flow rate.A1. Ru.

However, although the discharge pressure increases according to curve 1.2 of the characteristic curve in FIG. The output of the device 12 becomes positive. This value is
The signal is input to the PI calculator 13 and supplied to the high-order selector 6. As a result, when the input gradually increases and the output of the PI calculator 13 becomes larger than the command signal from the load demand, this increased signal replaces the command of the demand and becomes the water supply command to the water supply pump. Become.

Furthermore, this signal undergoes correction of the pump rotation speed with respect to the water supply command, and becomes the final water supply command 100a.

This water supply command 100a controls the flow rate control valve FV to increase the water supply flow rate to one water supply pump.

〔Effect of the invention〕

According to one embodiment of the present invention, the water supply flow rate during operation can always be kept larger than the limit value of the recirculation flow rate for ensuring the minimum flow rate of the water supply pump, so that the water supply to the water supply pump at low pressure can be maintained. Since the flushing phenomenon within the command is prevented, stable operation of the water supply pump is possible.

In addition, the water supply command is the discharge pressure of the water supply pump.

The flow rate of the water supply pump and the rotation speed of the water supply pump are detected, and within the control device, the command from the load demand is independently processed, and the water supply command from the load demand is controlled by taking correction into account. In case, any one
Even if a failure occurs in the detector system and its arithmetic unit, plant operation can continue without any hindrance.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the preconditions of the present invention, FIG. 2 is a system diagram of an embodiment of the present invention, and FIG. 3 is a system diagram showing a more detailed control method of the present invention. [)...Water pump, I'V...Flow rate adjustment...
RV...Recirculation meteor control valve, I) arithmetic unit,
2... Setting device, 3... Switching device, 5, 7.12...
Addition calculator, 6...High-level selector, 11.21...Function generator 1.100...Control unit, Bonami amount $2 diagram

Claims (1)

[Scope of Claims] 1. In a water supply pump control system in which a water supply command is given to a water supply pump provided for controlling the water supply flow rate to supply water, the water supply pump itself is prevented from operating in a dangerous area. A control method for a water supply pump, characterized in that the water supply command is a water supply command that enables operation outside a dangerous area. 2. In claim 1, the discharge pressure, water supply flow rate, and pump rotation speed of the water supply pump are detected, and the re@recirculation limit value of the pump is determined based on the pump flow rate-pump discharge pressure characteristic of the water supply pump. Based on the curve, determine the flow rate limit value corresponding to the discharge pressure detected above, calculate the deviation between the obtained flow rate limit value and the detected flow rate, compare the water supply command based on the load demand, and adjust the rotation speed. The above water supply cylinder is also corrected by
A water supply pump control method characterized by performing water supply control.