RU1788307C - Pressure regulation process for power unit steam generator - Google Patents

Abstract

Usage: automatic control systems for steam generators of power units. SUMMARY OF THE INVENTION: In a method for controlling pressure in a steam generator of a power unit by measuring pressure in a steam generator, turbine power and rotational speed of a turbine rotor, changing the flow rate of steam into a turbine, the invention relates to regulating and protecting power machines of the type steam generator – turbine – generator and can be used on heat engines and nuclear power plants. There is a known method of pressure protection in a steam generator in the event of an electrical load drop, based on a decrease in the heat capacity of the steam generator by reducing fuel consumption, on the steam discharge through the switchgear and on the opening of the steam generator safety valves according to the signal on the steam pressure in the steam generator when the first set value with correction is reached according to the frequency of rotation of the turbine rotor, changes in the set value of the turbine power and a decrease in fuel consumption when the power and circulation pumps are turned off c and reaching the pressure in the steam generator of the second predetermined limit value of less than the first additional value, a third pressure limit value is formed, less than the first and greater than the second pressure and equal to the current pressure value at the time of the operator’s command and maintained by changing the steam flow rate to the turbine at the current values pressure and power and the first power setpoint, after turning off the feed pump, the first pressure limiting pressure setpoint with correction for a signal for setting the speed of power reduction, and when the circulation pump is turned off, for a second set power value with a correction for the rotor speed. 8 ill. pressure increase. The disadvantage of this method is that it cannot be used to control the pressure in the steam generator when it decreases. This disadvantage is deprived of the known method of regulating the pressure in the steam generator of a power unit containing a turbine with control valves, feed and circulation pumps, by measuring the current pressure in the steam generator, the current power of the turbine and the rotational speed of the turbine rotor, and the change in the flow rate of the steam in the boiler. Vj 00 00 CJ о 4

Description

the turbine with control valves to change the steam pressure in the steam generator when it decreases to the first maximum value with correction for the frequency of rotation of the turbine rotor, change the set value of the turbine power and reduce fuel consumption when the circulation or feed pumps are turned off and the pressure in the steam generator reaches the second specified limit value , in size less than the first.

A disadvantage of the known method is the limited ability to regulate pressure within predetermined limits in various modes of operation of the steam generator due to the use of a limited number of pressure settings and the non-optimal composition of the control signals. The non-optimal composition of the control signals leads to a deterioration in the quality of the pressure control processes in the steam generator during an emergency shutdown of the feed or circulation pumps; this ultimately leads to a decrease in control accuracy, reliability and maneuverability of the power unit.

The purpose of the invention is to improve the accuracy of regulation and the reliability of the power unit.

The essence of the invention lies in the fact that in the method of regulating the pressure in the steam generator of a power unit containing a turbine with control valves, the feed and circulation pumps, by measuring the current pressure in the steam generator, the current power of the turbine and the speed of rotation of the turbine rotor, changing the flow of steam into the turbine by the control valves by changing the vapor pressure in the steam generator when this pressure reaches the first predetermined limit value with correction for the frequency of rotation of the turbine rotor, according to the invention, a third pressure value is set, by a value less than the first and greater than the second and equal to the current value of pressure, when the circulating or feed pumps are turned off and the pressure in the steam generator reaches a second predetermined limit value, which is smaller than the first, according to the invention at the time of issuing the operator’s command, and support it by changing the steam flow rate to the turbine according to the current pressure and power values and the first set power value, according to after shutting down the feed pump, the first pressure limit value s is maintained

correction according to the signal for setting the power reduction rate, and when the circulation pump is switched off, according to the second set power value with correction according to the rotor speed.

Figure 1 is a flowchart of an implementation of a control method; Fig. 2 - modules of a turbine control system; Fig. 3 - structure of one of the modules of the control system; Fig. 4 is a diagram of the effect of modules of a turbine control system in the RD1 mode; Figures 5, 6, 7 and 8 are diagrams of the action of the modules of the turbine control system, respectively, in the modes RD2, RDM, RD1M (modification RD1) and TK.

The steam generator 1 with circulation loops in which the circulation pumps 2 are located, supplying the working fluid to the heating element 3, generates steam, the flow rate and parameters of which are regulated by the fuel body 4, by the feed valve 5, which regulates the flow of feed water entering the steam nerator through the feed pump b, and the control valves of the turbine 8 (figure 1).

As a steam generating unit with elements 1-5, there can be single-circuit, double-circuit and three-circuit plants using nuclear and fossil fuels.

The fuel regulatory body of the 4 steam generators of nuclear power units is the CPS rods, and the fuel regulatory body of the 4 steam generators of fossil fuel power units is the fuel flow regulating body (e.g. coal, gas).

Steam from the steam generator 1 flows through the control valves 7 into the turbine 8, on the shaft of which there is a generator 9.

The automatic control system (ATS) 10 of the turbine receives signals:

the first and second maximum pressure values, respectively, Pzad1, Pzad2, in the steam generator 1;

the first and second predetermined power values of the turbine 8, respectively N3afl1, N3afl2;

a predetermined value fsafl of the rotor of the turbine 8;

tasks on the rate of reduction of thermal power -, rear steam generator 1;

according to the current power N of the turbine 8;

according to the current pressure P in the steam generator 1;

at the current rotational speed f of the turbine rotor 8.

The system 10 acts through a servomotor 11 on the control valves 7, ensuring the operation of the power unit in various modes of regulation of frequency, power and pressure,

As a signal for the current power N of the turbine 8, there may be a signal for the steam power of the turbine, for the electric power of the generator 9, for the vapor pressure in the intermediate stages of the turbine.

The steam power signal of turbine 8 is defined as the sum of the readings of the steam pressure sensors in the turbine stages. The signal for the electric power of the generator comes from the electric power sensor installed on the generator.

A signal f at the current rotational speed of the turbine rotor is supplied from a rotational speed sensor mounted on the turbine rotor 8; at. in case of operation of the power unit in the frequency and power control mode of the electric network, the frequency sensor of the electric network can be used as a frequency sensor.

The values of P3ad1, M3ad1 are greater than the corresponding values of P3ad2, N3afl2.

Signals P, N, f-analog type.

d N3aflT

Values P3ad1, P3, d2,

dt

-, f

ass

N3aA are set by the operator.

The values of Li3ad2 are set automatically upon a signal from automatic protection 12.

The automatic protection (A3) 12 of the steam generating equipment receives a signal v to turn off the circulation pump 2 and a signal V2 to turn off the feed pump 6.

A3 12 produces:

discrete (yes-no type) signals n and L2, respectively, to turn on the TZi RDM1 modes;

power reference signal Nsap.2 in TK mode;

analog or discrete signal for switching on the thermal power limitation system TK.

Signals l- | are generated by signal vi;

signals L2, Ls are generated by signal V2,

The system 13 for limiting the thermal power of the steam generator 1 acts through the fuel regulator 4 to reduce heat generation in the heating element 3. The system 13 can receive signals from the pressure in the steam generator 1, from the neutron power of the heating element 3, and from the average

the temperature of the primary coolant, defined as the arithmetic average of the temperatures of the coolant at the inlet and outlet of the heating element 3. The signal lz acting on the system 13, depending on the design of the system 13 and A3 12, can be:

a discrete signal that connects to the system 13 a specific analog task M3adt for thermal power of the steam generator 1;

the analog signal of the reference Izadt for the thermal power of the steam generator, the value of which is generated by the system 12. As the signal Izazd can be:

neutron power task in the heating element 3;

task on the average temperature of the coolant of the 1st circuit.

The value of M33dt in the TK and RD1M modes is less than in the previous E modes (RD1, RD2idr.).

Different ways of generating signals L1, L2, LZ, Mzad2, No add, V, V2 And circuits

embodiments of systems 13 and A3 12 are set forth in 1-3, 5.

ATS 10 includes modules (FIG. 2): determining the conditions and issuing a command to turn on mode 14 (RD1 or RD2, or RDM, or RDS, or TK, respectively, in FIGS. 4-8);

control signal selection 15; unshocked transition 16: selection of settings 17. Module 14 includes submodules (Fig. 3): automatic determination of the conditions for enabling mode 18;

issuing a command to enable mode 19;

storing the current pressure 20 (in the RDM mode of Fig. 6).

Submodule 18 determines the automatic activation of the modes RD1 and RD2 when the pressure P reaches the settings respectively Rzad1 and P3ad2 (Fig. 3).

Submodule 19 issues discrete commands (signals) A (Ai, A2, Az, A-, As) to turn it on (Fig. 3):

RD1 mode by signal from submodule 18 as an AI command;

RD2 mode by signal from submodule 18 in the form of command A2;

RDM mode at the operator’s signal in the form of the Az command;

RDSH mode by signal l as an A4 command;

TK mode by signal n in the form of an As command.

Module 15, upon command A from submodule 19 of module 14 on switching on the operation mode (FIGS. 2, 3), includes a certain combination of control signals for the included operation mode from the total number of control signals supplied to the input of module 15, namely:

at At command - signals f, tzad, P, Rzad1 of the RD1 mode;

by command A2 - signals P, Rzad2, f, faafl of the RD2 mode;

at the command Az - signals P, N, M3ad1, f, fsafl of the RDM mode;

by command A4 - signals f, P, P3ad1,

d Mzadt

dt

-, faafl mode RD1M;

at the command Hell - signals N, M3ad2, f, tzad of the TK mode.

Module 16 of the shockless transition by command A from submodule 19 of module 14 on the activation of the corresponding mode (Fig. 2,3) produces an analog signal of type a, (ai, 32, az, 34, as) (Fig. 2), the amplitude of which is equal to the value that is required to compensate for the residual control signal from the previous operating mode, and when the RD1 or RD2, or RDM, or RDM1 or TK mode is turned on, an additional signal is generated ai, 32, az, 34, as, respectively (Figs. 4-8) . Then, at the moment of a shockless transition to any of the above modes, the total signal at the output of module 16 is zero, and switching to the corresponding mode is carried out smoothly.

Module 17, upon a command from submodule 19 of module 14 on the activation of the corresponding mode (Fig. 2,3), generates the PI control law with a different composition of control signals and various optimal numerical values of the settings depending on the mode, namely: in the RD1, RD2 mode , RDM, RDM1M, TK the law of regulation has the form of equations, respectively: 1, 2, 3.4 and 5

P M - (Mzad1 - N) + (P - RzadZ) +

+ (N3aAl N) + + RT (p RzaAz)

(3)

1 ° / -ru (P - RzadO + / (P - Rzad1) oCH - 1 f d d Mzadt / d t d Mzadtn / Y t

 .- $ - (No.ad2 N) (NsaA2

-N) (4)

(5)

0

5

0

5

 :

T;

ass

ass

j- (i is the movement of the valves of the turbine 7 in relative (dimensionless) units, in which the value equal to one corresponds to the fully open position of the valves, and the value of /, equal to zero, is completely closed;

Ki, I 1 ... 3; Ti (C) i 1 ... 5; di. I 1. 2 - numerical values of the settings; Ki, 5i - dimensionless;

Pi, Rn, Rzad1, Rzad2 kg / cm2 - respectively current, at the nominal operating mode of the power unit, the first maximum set pressure, the second maximum set pressure value;

N, N3afli, M3ad2 MW - respectively, the current, in nominal mode, the first set, the second set value of power;

f, faaA Hz - respectively, the current, set frequency value;

p - frequency deviation in relative units;

d Izadt d N3aflTH | MBT

dt

dt

- corresponding

, (r-rzad1) +

+ -gGy - / (P-Rzad1) aCh-4

g

R

T1 Rn (R-Rzad2) +

 N

+ -fiV / ()

the value of the task in terms of the rate of decrease in thermal power in the RD1M mode, the nominal (typical) value of the task in terms of the rate of decrease in thermal power during operation of the power unit in the frequency and power control modes of power systems;

d Mzadt / d Mzadtn

-. / --- t- - - task value

according to the rate of decrease in thermal power in relative units.

The numerical value of the parameters in equations (1-5) for power units of nuclear power plants and thermal power plants lie in the range:

About Ki 100, i 1 ... 5; 1 Ti 200, I- 1 ... 5; 0.01 5i 1, i 1.2;

1 d Mzadt / d Mzadtn 1QQ d t / d t

which is established by the methods of mathematical modeling and operating experience of power units.

For each type of power unit and for each operating mode, the optimal numerical values of the parameters from the above limit are determined by mathematical modeling methods and operating experience of the power units.

Figure 2 shows that the output of module 15 is the input of module 16, the output of which is the input of module 17. In general, these modules can be a single unit, and the order of their interconnection can be different.

Modules and submodules 14-20, CAP 10, A3 12 and system 13 can be implemented on an analog, digital, microprocessor element base, in the form of local controllers, micro-mini-computers. For example, module 15 can be implemented on elements such as an encryptor-decoder, module 16 - on elements of comparison and storage, module 17 - on elements of amplification, integration and control, submodule 18 - on elements of comparison, submodule 19 - on elements of control, amplification tracking, comparison, submodule 20 - on the memory elements.

The method is carried out as follows.

When the pressure P in the steam generator decreases to the first limit set value P3ad1 set by the operator, submodule 18 of module 14 gives a command to turn on submodule 19. The last one gives an AI command by the above command or by command of the operator to turn on modules 15, 16 and 17 at the same time, which leads to turn on the control system 10 in the RD1 mode (Fig. 4).

Module 15, at the AI command, selects the signals P, Rzad1, faafl, f FROM the GENERAL NUMBER of control signals used at the input of the module and supplies them to the input of module 16.

Module 16, upon the AI command, generates ai signal, which compensates for the residual control signal from the previous operation mode,

Module 17, at the AI command, sets the control law according to equation (1) and the numerical values of the settings (Kj, TI, 5j) that are optimal for the RD1 mode.

The total control signal, passing the modules 15-17 of the system 10, impacts the servomotor 11, which, by closing the control valve 7, ultimately changes the position of the valve 7 so that the pressure in the steam generator 1 in the RD1 mode is maintained at the level of Rzadt ; wherein the position of the valve 7 is corrected by the signal about the rotational speed of the rotor, representing the difference of the signals of the set and the current value in the frequency Mzad.

When the pressure P in the steam generator decreases to the second maximum preset value Pzad2 set by the operator and lying below the first P3ad1 and the third Pzadz, submodule 18 gives a command to turn on submodule 19. The latter gives a command A2 to turn on modules 15, 16 and 17 at the same time, which leads to turning on the control system 10 in the RD2 mode (Fig. 5).

Module 15 selects P. P3ad2 signals. f, fsafl and feeds them to the input of module 16.

Module 16 generates a shockless transition signal 32.

Module 17 sets the control law according to equation (2) and the numerical values of the settings that are optimal for the RD2 mode.

The total control signal, passing modules 15-17, shocklessly acts on the servomotor 11, which, covering the valve 7, eventually changes the position of the valve 7 so that the pressure in the steam generator 1 in the RD2 mode is maintained at the level of Rzad2, while the valve position 7 is corrected by the rotor speed signal.

At the operator’s command to activate the RDM mode (Fig. 6), the submodule 19 gives the command Az to simultaneously turn on the modules 15-17 and the submodule 20.

Module 15 generates signals P, N, N3afli, f, fsafl and feeds them to the input of module 16.

The module 20 stores the pressure value P in the steam generator at the moment of the inclusion of the RDM mode, which becomes the third maximum set value Rzad and which is supplied to the input of the module 16.

Module 16 generates an unstressed transition signal.

Module 17 sets the control law according to equation (3) and the numerical values of the settings that are optimal for the RDM mode,

The total control signal, passing modules 15-17, shocklessly acts on the servomotor 11, which, covering the valve 7, eventually changes the position of the control valve 7 so that the steam pressure in the steam generator is maintained at the level of Razad according to the static pressure-power characteristic, at in this case, the position of the valve 7 is corrected by the signal of the rotor speed.

The presence of RDM signals in the current power mode, the first preset value for power, the third maximum preset value for pressure, less than the first and greater second, determined by remembering the current pressure in the steam generator at the moment the mode is turned on, and at the same time combining the signals the current pressure in the steam generator and the power that are not available in the modes RD1 and RD2, leads to an improvement in the quality of the transition process compared to the prototype and the modes RD1 and RD2 (reduced and pressure relative to the set value by 5-10% and decrement of pressure attenuation, defined as the ratio of the subsequent amplitude to the previous one, by 10-20%) and ultimately to increase the accuracy of regulation, maneuverability and reliability of the steam generator, which is expressed in reducing the time just a steam generator.

In the event of an emergency shutdown of one of the feed pumps 6, the flow of feed water through the valve 5 decreases. In this case, the RD1M mode is turned off according to the following scheme (Fig. 7). ...

The shutdown signal Vz of the pump 6 affects the actuation of A3 12, which generates a signal, acting through the system 13 and the organ 4 to reduce the thermal power of the element 3.

At the same time, A3 12 generates a signal to turn on submodule 19. The latter issues an Az command to simultaneously turn on modules 15-17.

Module 15 selects the signals f, t3ad, P,

d Gzzalt

RzadCh, -. and feeds them to the input of module 16.

Module 16 generates a signal az.

Module 17 sets the control law according to equation (4) and the numerical values of the settings that are optimal for the RD1M mode.

The total control signal, passing modules 15-17, shocklessly acts on the servomotor 11, which, covering the valve 7, ultimately changes the position of the valve 7 so that the pressure in the steam generator 1 in the RD1M mode is maintained at the level of Rzadz, while the position of the valve 7 is adjusted by a signal according to the rotational speed of the rotor.

The presence of additional exposure

d Izadt

dt

in RD1M mode, aimed at

faster closing of the valves 7 in the initial time interval for switching on the mode than covering in the modes RD1, RD2,

RDM in the prototype, and consistent with the effect through the system 13 to reduce heat in the heating element 3, leads to a decrease in overshoot in pressure in the steam generator by

10-20% relative to the first limit value compared with the modes RD1, RD2, RDM and the prototype. This ultimately leads to an increase in control accuracy and an increase in the maneuverability and reliability of the steam generator, which results in a reduction in the time of the simple steam generator.

In the event of an emergency shutdown of one of the circulation pumps 2, the TK mode is activated according to the following scheme (Fig. 8).

The signal vi about the shutdown of the pump 2 affects the operation of A3 12, which generates a signal, acting through the system 13 and the body 4 to reduce

thermal power element 3.

At the same time, A3 12 generates a signal of the second predetermined value in terms of power MEad2, which is smaller than the first Nsafli, which is input from module 19.

At the same time, A3 12 generates a signal to turn on submodule 19. The latter issues an Az command to simultaneously turn on modules 15-17.

Module 15 generates signals M3ad2, N, f, Tzad and feeds them to the input of module 16. Module 16 generates a signal 35. Module 17 sets the control law according to equation (5) and the numerical values of the settings that are optimal for the TK mode.

The total control signal, passed modules 15-17, impacts unstressed on the servomotor 11, which, covering

the control valve 7 ultimately changes the position of the valve 7 so that the pressure in the steam generator 1 is within acceptable limits and the current power of the turbine 8 corresponds to a given L3ad2, while the position of the valve 7 is corrected by the signal about the rotor speed. The activation of the TK mode when the pump 2 is turned off with signals for the current turbine power, for the second set value of the turbine power, smaller than the first one, aimed at reducing the flow of steam to the turbine by closing the turbine valves in accordance with the effect through the system 12 to reduce heat generation in the heating element 3, leads to a reduction in settlement suppression in the steam generator by 15-25% compared with the modes RD1, RD2, RDM and the prototype. This ultimately leads to an increase in the accuracy of regulation, maneuverability and an increase in the reliability of the steam generator and to a reduction in its time.

Claims (1)

SUMMARY OF THE INVENTION A method for controlling the pressure in a steam generator of a power unit comprising a turbine with control valves, a feed and circulation pumps, by measuring the current pressure in the steam generator, the current turbidity of the turbine and the speed of rotation of the turbine rotor, the change in the flow rate of steam into the turbine by control valves to change the pressure of the steam in the steam generator when it reaches the value of the first predetermined limit value with correction for the frequency of rotation of the turbine rotor, changes in the set value of power turbines and reducing fuel consumption when the circulation or feed pumps are turned off and the pressure in the steam generator reaches a second predetermined limit value less than the first one, characterized in that, in order to increase the accuracy of regulation and reliability of the power unit, a third pressure limit value is set, less than the first and more than the second limit value, and equal to the current pressure value at the time of supply operator’s commands, and support it by changing the flow rate of the steam to the turbine according to the current pressure and power values and the first set power value, after turning off the feed pump, they maintain the first limit set pressure value corrected by the signal for setting the power reduction speed, and when the circulation pump is turned off, by a second setpoint value of power with correction according to rotor speed. L  Ј / .. /4 D / g I A JrfjaC / tt /9 / 7 w // L. -g P AtWtAzAtAsl W7 I I g / 7 J Fig.Z