JPS5936163B2 - Water pump drive turbine speed control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a feed water pump driven turbine speed control device, and more particularly to a speed control device for a turbine equipped with an electric speed governor.

In water supply flow rate control, the flow rate index () is determined by the load demand.

For example, in the case of a power generation plant, the required water supply amount for the boiler is determined by the load demand of the main turbine, and becomes the discharge flow rate command for the boiler feed water pump.

This demand signal changes from 0 to 100% depending on the load, but the pump must ensure a minimum flow rate as long as it is rotating to prevent heating.

This lowest flow rate is called the minimum flow.

However, if the load demand is less than the minimum flow,
The minimum flow of the pump cannot be ensured.

In addition, due to the need to suddenly reduce the water supply to the boiler side due to load shedding, etc., a relief valve is installed to ensure the minimum flow of the pump at low loads, and to bypass and release the water supply to the boiler side due to load shedding etc. .

This relief valve is normally open when the load is above the minimum flow, so when the boiler/turbine is started and the load increases, the relief valve is fully closed due to the demand above the minimum flow.

This relief valve normally operates on and off, and when it closes, the amount of water supplied to the boiler increases by the capacity of the relief valve, resulting in an unfavorable condition for the boiler.

A device as shown in the block diagram of FIG. 1 has been proposed as a feed water pump and driving turbine speed control device that corrects the boiler feed water flow rate by opening and closing the relief valve.

The error signal between the flow rate request command signal and the actual flow rate signal from the pump suction flow rate detector 1 passes through the signal converter 4 and becomes a flow rate request signal.

This flow rate request signal passes through the morph control circuit 5 and drives two control morphs.

The position signal output of the control motor 6 is transmitted to the turbine speed detector 1.
The error signal is compared with the turbine actual speed detected in step 1, and the error signal is passed through the calculation section 7 to open and close the steam control valve 8.

The steam flowing through the steam control valve 8 rotates a turbine 9, drives a pump 10 directly connected to the turbine 9, and obtains a required water supply flow rate.

Here, when increasing the load from a low load, the relief valve is closed when the flow rate 14 is higher than the minimum flow of the pump 10, and the bias is set by the contact 3, which closes in conjunction with the closing of this relief valve Il-. This is to correct the increase in the boiler side flow rate due to the closure of the relief valve by using the bias signal that reduces the water supply flow rate by utilizing the power supply unit 2.

However, the bias setting device 2 is located outside the speed governor 14a,
The step signal from the bias setter 2 is a flow rate bias signal and is delayed due to the integral characteristic of the signal converter 4, and the motor control circuit 5, which controls the control motor 6 with the bias signal, The arithmetic unit 21 receives the bias signal and converts it into a position command signal for the control motor 6.

This position command signal is a signal detected by a motor position detection circuit consisting of a differential transformer 24 that converts the position of the control motor 6 into an AC voltage proportional to the position, and a demodulator 25 that converts the AC voltage into a DC voltage. compared to

This error signal is used to drive the control motor 6 through the control calculator 22 and the power amplifier 23 that amplifies the power of its output.

The control motor 6 itself has an integral characteristic, and the control motor 6 as shown in the motor control circuit 5
The transfer characteristic from A to B of the motor position control portion including position feedback is a first-order lag.

For this reason, coordinated correction is not possible.

The present invention was developed as a result of considering the above-mentioned problems, and its purpose is to provide a coordinated turbine speed control device for driving a water supply pump.

In order to achieve the object, the present invention includes a computing unit that converts an error signal between a flow rate command value and an actual flow rate into a turbine speed signal corresponding to a required flow rate signal; A signal converter that converts into a signal; a servo valve that receives an error signal between the output of the signal converter and a detected value of the turbine speed detector; and a servo valve that converts the output of the servo valve into a hydraulic signal; A steam power reduction valve, a turbine that receives the output of the steam power reduction valve and rotates at the same time, and a contact that turns on when the pump discharge flow relief valve opens and turns off when the pump discharge flow relief valve opens. and a bias setting device that applies a bias signal for preventing a change in the boiler input flow rate to an error signal between the output of the signal converter and the detected value of the turbine speed detector.

The present invention will be explained in detail below.

FIG. 2 is a block diagram of a turbine speed control device for driving a water pump according to the present invention.

The water supply flow rate command is compared with the actual flow rate signal detected by the pump suction side flow rate detector 2, and the error signal is input to the speed governor 14b.

This input signal passes through a signal converter 4 and becomes a speed setting signal proportional to the water supply flow rate signal.

This speed setting signal is compared with the actual turbine speed signal detected by the turbine speed detector 11 to detect the speed of the turbine '9, and the error signal passes through the calculation section 12 and becomes an oil pressure signal at the servo valve 13. The steam power reducing valve 8 opens and closes depending on the duty.

The steam flowing through the steam power reduction valve 8 rotates a turbine 9, which is directly connected to the turbine 9, and drives a pump 10, thereby obtaining a desired water supply flow rate.

Here, when the load requires a flow rate demand higher than the pump minimum flow at low load, the speed governor 14b closes the relief valve, and a bias setting device is connected to the speed governor 14b via the contact 3 that closes under the condition that the relief valve is closed. 2 is provided, and the bias signal from the bias setting device 2 becomes a signal that corrects the speed setting signal proportional to the flow rate command from the signal converter 4 by the minimum flow amount, increasing the speed and correcting the boiler side flow rate. .

This negative bias signal is directly added to the input of the servo valve 13 as a step signal, and since the servo valve 13 itself has good coordination with little delay, it is possible to immediately correct the speed, that is, the boiler side feed A (flow rate). I can do it.

As described above, the feed water pump drive turbine speed control device according to the present invention uses a bias signal to correct the change in the boiler input flow rate due to the opening and closing of the pump discharge flow relief valve at low load. By adding error signals to the detected value, the flow rate change width is suppressed, and the bias signal is directly applied to the servo valve as a step signal, and since the servo valve itself has good coordination with little delay, it can be adjusted immediately. It is possible to modify the speed, that is, the boiler side water supply flow rate.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional turbine speed control device for military water supply pumps, and FIG. 2 is a block diagram of a turbine speed control device for driving a water supply pump 1 according to the present invention. 1... Pump suction flow rate detector, 2...
Bias setting device, 3... Contact, 4...
Signal converter, 5...Morph control circuit, 6...
...Control motor, γ, 12゜21...Calculation unit, 8...Steam 710 valve reduction, 9...
Turbine, 10...Pump, 11...
Turbine speed detector, 12... calculation unit, 13.
...Servo valve, 14a. 14b... Speed governor, 22.../Aj+
JiYi'p Enshinki, 23... Power amplifier, 24.
...Differential transformer, 25...Demodulator.

Claims (1)

[Claims] 1. A computing unit that converts an error signal between the water supply flow rate command value and the detection value of the pump suction flow rate detector into a turbine speed signal corresponding to the required flow rate; and a computing unit that converts the output of the computing unit into a required flow rate signal. a signal converter, a servo valve that receives an error signal between the output of the signal converter and a detected value of the turbine speed detector and converts it into a hydraulic signal, and a steam control valve that receives the output of the servo valve and operates to open and close. , a rotating turbine receives the output of the steam 7JO valve reduction, and receives the output of the turbine;
A bias signal for preventing a change in the boiler input flow rate is connected to the output of the signal converter and the pump to be driven, and a device that turns on when the pump discharge flow relief valve opens and turns off when the pump discharge flow relief valve opens. A feed water pump drive turbine speed control device consisting of a bias setting device that responds to an error signal with respect to the detected value of a turbine speed detector.