SU1746123A1 - Method of steam generator water level control - Google Patents

Abstract

Use: in heat and power engineering at regulation of water level in the steam generator. Summary of the Invention: Modify feedwater flow. At the time ti, when the deviation of the water flow from the steam flow reaches a predetermined value, the comparator 16 is triggered and the time interval forming unit 17 is started. This block produces a pulse proportional to the absolute value of the level deviation at the time ti. Now, during the time interval At, the regulator 11 changes the degree of opening of the valve 5 and thereby eliminates the deviation of the water level from the set value. After the time interval At, the switch 10 connects the output of the amplifier 14 to the input of the controller 11 and the adjustment process is cyclically repeated. 2 Il.

Description

is smiling

you

The invention relates to a power system and can be used to automate the control of nuclear steam generators and boilers of thermal power plants.

There is a known method for adjusting the water level in a boiler drum by changing the water flow rate according to the algebraic sum of the measured values of water flow, steam and the water level in the boiler drum.

The closest technical solution to the invention is the method of adjusting the water level in the boiler drum by changing the water consumption according to the algebraic sum of the measured values of the water level in the boiler drum and the previously differentiated consumption of steam and water.

The disadvantage of this method is the low quality of the water level control.

The purpose of the invention is to improve the accuracy of water level control in a steam generator.

The goal is achieved by first regulating the feedwater flow rate, determining the deviation of the feedwater consumption from the steam flow, and when this deviation reaches the specified value, determining the deviation of the feedwater level, and then changing the water flow at a given rate in the direction of reducing the level deviation, after which the adjustment process is cyclically repeated.

Figure 1 shows an automatic water level control system in a steam generator; FIG. 2 is a structural diagram of a unit for forming a time interval, implementing this method.

The automatic water level control system (Fig. 1) contains a steam generator 1 with a water level sensor 2 and a steam consumption sensor 3 installed on it, connected to the steam generator 1 feedwater pipe 4 with a control valve (RPC) 5 and feed sensor 6 water inlet to the steam generator, connected in series the first unit 7 of the signal, the first device 8 comparison, the first amplifier 9, two-channel switch 10, regu lur 11, the actuator (servo) 12, output associated with RP To 5, the second comparator 13, serially connected, the second amplifier 14, the output connected to the second input

switch 10, serially connected third signal setter 15, comparator 16, time interval forming unit 17, output connected to the third (control) input of switch 10, the second input of the first comparison device 8 connected to the water level sensor 2, the first and second inputs the second comparison device 13 is connected

respectively, the steam and water consumption sensors 3 and 6, the second input of the switch 16 is connected to the output of the second comparator 13, and the second input of the time interval forming unit 17 is connected to

the output of the first device 8 comparison.

The time interval forming unit 17 (Fig. 2) comprises a pulse generator 18 connected in series, an AND 19 logic element, a pulse counter 20,

a digital-to-analog converter 21, a comparator 22, output connected to a second input of an element 19, serially connected to a signal module module allocator 23, memory block 24, output

connected to the second input of the comparator 22, the second inputs of the pulse counter 20 and the memory block 24 are the first input of the block 17, the second input of which is the input of the signal modulator selection device 23, and the output of the block 17 is the comparator output 22.

The automatic control system works as follows.

The feed water enters the steam generator 1 through line 4 through the regulating feed valve 5. When the flow rate G of water entering the steam generator 1 deviates from the flow rate D of steam from it, the regulator 11 is ei from the second device 13

the comparison associated with the sensors 3 and 6 of the flow rate of steam and water, using an actuator (servo) 12, changes the degree of opening of the valve 5 and thereby changes the amount of

The steam generator 1 feed water and eliminates the deviation of the water flow G in the steam generator 1 from the consumption of steam D from it. In this case, from the time interval formation unit 17, a logical zero signal is sent to the control input of the two-channel switch 10, and therefore only the signal Јi G-D comes to the input of the controller 11 through the second amplifier 14. At the time ti, when the deviation of water consumption from steam consumption

will reach the specified small value, i.e. when I Јil (5i const. operates the comparator 16 and starts the block 17 for forming the time interval, which since time Ti gives a pulse of a logical unit of length At proportional to the absolute value of the deviation of water level I and (ti) I.in the steam generator at time t1 from the given values, i.e.

 I Ј 2 (tl) I,

where K is the proportionality coefficient.

During the time interval A t, the switch 10 now, using the signal from block 17, connects the output of the first amplifier 9 to the input of the controller 11, which, under the influence of the amplified signal 2, coming from the output of the second comparison device 13 connected to the water generator 2 of the steam generator 1 , by means of the actuator 12, changes the degree of opening of the valve 5 and thereby changes the amount of feed water entering the steam generator 1 and eliminates the deviation of the water level from the set value. When the time interval At has expired, the switch 10, according to the signal from block 17, connects the output of the second amplifier 14 to the input of the controller 11 and the adjustment process is repeated cyclically.

The time interval shaping unit (Fig 2) operates as follows.

Under the action of the signal from the output of the comparator 16, the pulse counter 20 is reset to the initial zero state, and the memory block 24 stores the current value of the signal module I Ј 2 (ti) I from the output of the module allocator 23 and supplies it to the comparator input 22. After that, the pulses from the output of the generator 18 through the element And 19 fill the counter 20 pulses. Voltage at digital-to-analog output

until it reaches the voltage supplied from the memory block 24.

At the moment of equality of these voltages, the comparator 22 is activated, prohibiting

the most complete filling of the counter is 20 pulses. The output value (logical zero) remains unchanged until a new pulse arrives from the comparator 16. The value of the interval At K | Ј2 (ti) I

governed by the frequency of the pulses from the output of the generator 18.

The use of the method allows to improve the quality indicators of the water level control system in the steam generator at

action of disturbances in steam and feedwater consumption, which ultimately leads to increased reliability and durability of the equipment of the power unit.

Claims (1)

Invention Formula The method of adjusting the water level in the steam generator by changing the water flow rate according to the measured flow rates steam, water and level, characterized in that, in order to increase reliability by reducing the frequency of actuating the actuator, first regulate the flow of feed water and at when the deviation of feedwater consumption from the steam flow of a given value is reached, the deviation of the feedwater level is determined, and then during the time interval proportional to this deviation the water consumption is changed at a predetermined rate in the direction of decreasing the level deviation, after which the adjustment process is cyclically repeated .