JPS6224608B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control system for a power generation plant, and more particularly to a control system for a fossil fuel power plant such as those found in modern central power plants. When nuclear power generation equipment comes into operation, other equipment in the system is used as a low-load system because nuclear power generation equipment is used at a constant load due to low fuel costs and operational limitations. It must be able to withstand frequent and rapid load fluctuations, including complete shutdowns. For example, typical cycling equipment has an initial steam condition of 2400 psig (168.72 Kg/cm ² ) 1000
(537.8℃) and is rated between 400 and 600MW. In such systems, steam typically passes first through a high-pressure turbine, then through a reheat path in a steam power generator that raises the steam to a high reheat temperature of 1000°C (537.8°C), then through an intermediate-pressure turbine, a low-pressure turbine, and a condenser. flows to

Such devices can be operated at part load for very long periods. It is therefore an object of the present invention to program the throttle pressure according to the load, thereby increasing the thermal efficiency of the system and allowing rapid load changes without thermal shock to the turbine while maintaining steam in the turbine impulse chamber throughout the entire load range. The object of the present invention is to provide a control device that keeps the temperature substantially constant.

The above and other objects of the present invention will become clear from the following description as well as the drawings.

The block diagram in FIG. 1 has a steam generator, ie, a boiler, designated by the reference numeral 1, and a turbine generator, designated by the reference numeral 2. A more or less conventional steam turbine power plant comprising: As shown in the drawings, the high-pressure turbine 3, intermediate-pressure turbine 4, and low-pressure turbine 5 drive one generator 6 to generate electricity, and the generated power is transmitted via conductors 7, 8, and 9. Alternatively, each turbine may drive a separate generator and send their generated power to a common conductor.
The particular configuration of the turbine generator used does not form part of the invention.

Steam discharged from the secondary superheater 10 of the steam generator 1 passes through the high-pressure turbine 3 and is sent to the reheater 11. The steam reheated at a high temperature by this reheater 11 passes through an intermediate pressure turbine 4, then a low pressure turbine 5, and is discharged to a condenser 12. capacitor 1
The condensate from 2 is removed by a condensate pump 13 to a series of low pressure heaters 14 where it is heated with extracted steam from the low pressure turbine 5 and sent to a degassing heater 15 where it is further extracted. Heated with steam. The feed water is drawn by the boiler feed water pump 16 from the degassing heater 15 to the high pressure heater 17, where it is heated with extracted steam, and in addition to the previously mentioned secondary superheater 10 and reheater 11, it is also supplied with an economizer 18, a furnace 19 and It is sent to a steam generator 1 equipped with a primary superheater 20. Flow control valve 1
6A is shown in the drawings as representing any one of a plurality of conventional control means that may be used to control the flow rate of feed water to the boiler.

FIG. 2 shows the basic form of the air gas cycle of the steam generator 1. Combustion air from forced air blower 21 passes through air preheater 22 and is supplied to furnace 19 . The fuel, which may be oil, gas, coal or a combination thereof, is supplied by any suitable means (not shown).
is supplied to the furnace 19 by. Combustion gases or commonly referred to as flue gases exit the furnace 19 and pass through the furnace 2
Passes through the secondary superheater 10, reheater 11, and primary superheater 2
0, passes through the economizer 18, air preheater 22,
Then, it passes through the induction fan 24 and is exhausted to the atmosphere from a chimney (not shown). The flue gas leaving the economizer 18 is also passed through a gas recirculation fan 25 as a means of controlling the temperature of the hot reheat steam delivered from the reheater 11 within some or all of the normal operating range of the system. It can be recycled to the furnace 19. Generally, the flow rate of the recirculated gas is
is retained in inverse proportion to the heat or energy input to it. The illustrated order in which the combustion products pass through the plurality of heating sections does not represent an exclusive order. This order is, for example, from the primary superheater 20 to the
The order may be from the secondary superheater 10 to the reheater 11, or from the secondary superheater 10 to the primary superheater 2.
0 to the reheater 11.

Bypass system includes primary and secondary superheaters 10, 20
and has a conduit 26, the inlet of which is connected to the inlet of the primary superheater 20;
The outlet of conduit 26 is also connected to a condenser 12 which condenses the steam conveyed through conduit 26 and returns it to the water supply system. Also as shown, a device is provided for distributing steam from conduit 26 through conduit 27 to the outlet of secondary superheater 10 and through conduit 28 to the outlet of reheater 11, respectively. Diversion of substantially saturated steam into superheated and hot reheated steam that feeds the turbine provides a means of mitigating the steam temperature required during start-up and low load operation. Become.

FIG. 3 shows a block diagram of a control device applied to the power generators shown in FIGS. 1 and 2. The illustrated control elements or hardware are commercially available and their operation will be well understood by those skilled in the art.
Furthermore, the control system is shown in block diagram form in order to avoid being limited to control systems with special types of control, such as pneumatic control, electronic or electric control, or a combination thereof. 1 and 2 only show the final control elements of the main controller shown in FIG. 3.
For further brevity, we have omitted the local feedback control loops associated with the final control elements, whose purpose is to maintain the value of the controlled variable in a predetermined functional relationship to the value of the control signal. . Also, control operations such as set point, addition, integration, etc.
It is assumed that differentiation and reset are included in the various control loops described above, if necessary.

When operating a cycling device (hereinafter, a device that generates steam to generate electricity and whose load changes appear in cycles is referred to as a cycling device), two types of startup are used: cold startup and hot startup. be. Irrespective of the boiler turbine conditions, i.e. hot, cold, or intermediate temperature, on-line operation ensures that the boiler burns to meet its most important requirements, and that auxiliary controls ensure that other This can be achieved most rapidly by satisfying the requirements. For example, in the case of a hot start, the steam generator and the boiler's primary superheater are at relatively high pressure and saturation temperature, while the secondary superheater and reheater are at relatively low temperatures; The most important requirement is the superheated steam temperature, so the boiler burns to increase this superheated steam temperature at the maximum permissible rate and, if necessary, the steam to maintain the boiler pressure at the desired value. can be drained into a capacitor. Conversely, in cold start conditions, the boiler must be heated to allow steam to flow. As a result, the steam temperature is increased when the turbine is cold. Thus, an important requirement in cold start conditions is the boiler pressure, which controls the combustion rate, while excessively high steam temperatures are reduced using steam and water attemperators. Regardless of the form of activation,
The controller automatically selects critical requirements and controls combustion and other critical conditions are maintained at set point values by the selected controller.

In FIG. 3, the load request signal of the device is inputted to the primary control signal generator 30 of the automatic load transmitting device 2.
9 or other automatic or manual device, the primary control signal generator 30 generates a feedforward control signal corresponding to the desired energy output of the generator. This feedforward control signal is transmitted via signal conductor 31 to load error correction device 32.
The load error correction device 32 sends a steam flow rate request signal to the conductor 33. The device 32 is also provided with a signal (considered a feedback signal) corresponding to the megawatt output produced by the transmitter 34, so that the device 32 receives the output power required to maintain the two incoming input signals equal. Generates a request signal.

The feedforward control signal is also connected to conductor 31.
A throttle pressure ramp generator 35 is also supplied via the throttle pressure ramp generator 35, which generates minimum pressure, maximum pressure, and ramp throttle pressure (ramp here refers to a slope, in other words, a constant speed change in pressure). Manual adjustment selectors 36, 38, and 37 are provided to set the respective settings. For example, the maximum throttle pressure is 2400psi
(168.7Kg/cm ² ), minimum throttle pressure is 600psi
(42.2Kg/cm ² ) and ramp throttle pressure from 20% to 70% of full load or 600psi (42.2Kg/cm 2 ).
cm ² ) to 2400 psi (168.7 Kg/cm ² ). In other words, the device 35
is 600psi (42.2Kg/
A turbine throttle pressure demand signal is generated via conductor 39 requesting a constant pressure of 70 cm ² );
A throttle pressure demand signal is generated that increases with increasing load demand until the % load point is reached, and then a signal corresponding to a constant pressure of 2400 psi (168.7 Kg/cm ² ) at full load is generated. Adjustment selector 36, 37, 3
8 allows the driver to arbitrarily set the maximum throttle pressure, minimum throttle pressure, and load span within the ramp.

The steam flow demand signal transmitted via conductor 33 adjusts the fuel flow control valve 40 and air flow control damper device 41 to maintain the energy input to the system in accordance with the energy demand. The steam flow demand signal is also sent via lead 33 to a turbine steam flow control valve 42 which maintains the steam flow to the high pressure turbine 3 in accordance with the steam flow demand signal. By performing variable pressure operation, the turbine flow control valve 42 remains approximately 70% open from the minimum pressure set as the 70% load point to the maximum pressure for the aforementioned minimum, maximum, and ramp pressures; It then changes proportionally as load demands increase. However, through minimum pressure and ramp pressure, the control valve 42 changes from the 70% open position where it immediately satisfies a request for an increase or decrease in steam flow, but only if such change in demand is satisfied by a change in combustion rate. 70
It is returned to the % open position. In other words, transient changes in load demands are met by drawing energy into and out of the boiler, and the energy storage is maintained at the desired level by appropriate changes in the firing rate.

The throttle pressure request signal is transmitted via conductor 39 to a throttle pressure and sequence device 43 which is also supplied with a signal proportional to the actual throttle pressure from a pressure controller 44 and which output signal is supplied to a position valve 46, which is provided between the primary superheater 20 and the secondary superheater 10 to maintain the throttle pressure at a desired value. In general, valve 46 may serve as a downstream pressure regulator to maintain the throttle pressure at the programmed value generated by device 35.

The throttle pressure program control signal is also routed via lead 39 to boiler pressure program control 47.
and also to the boiler pressure program controller 4.
7 is supplied with a signal proportional to the actual primary superheater outlet pressure from a pressure controller 48, and this boiler pressure program controller 47 generates an output signal that varies functionally with the turbine pressure;
This output signal is sent along line 49 to sequence controller 58 to adjust the combustion rate to maintain the steam pressure at the outlet of primary superheater 20 at a desired value.

During start-up, the combustion rate must be adjusted by various auxiliary controls to maintain the most important requirements at desired values and other conditions as well, as described above. One most extreme case is the so-called hot start-up, in which the boiler pressure through the primary superheater 20 is approximately at the desired value, and the other extreme is the so-called hot start-up, in which the boiler and turbine are at a low temperature. There is a cold start. Regardless of the startup method, the first thing you need to think about is:
This means that the difference between the steam temperature and the temperature of the metal parts of the turbine must be kept within tolerances, so that the steam and metal temperatures are raised as quickly as possible to prepare the equipment within a minimum time.

During start-up, regardless of cold, hot or intermediate temperature start-up, the device must meet the most necessary, but not limited, conditions of throttle pressure, secondary superheater 10 and reheater 11. It is necessary to carry out combustion so as to maintain the gas temperature at the steam outlet and the superheated steam pressure at programmed values.
For this purpose, for example, if the valve 46 is unable to satisfy the throttle pressure requirements, the conductor 5
A control signal is transmitted via line 53 to a high signal selector 52, to which the selector or selector 52 is supplied via a line 53 with a control signal proportional to the deviation of the gas temperature from the programmed value, and which is also supplied with a control signal proportional to the deviation of the gas temperature from the programmed value. A control signal proportional to the deviation from the programmed value is provided through conductor 54. The highest of these signals is provided via lead 55 to summing device 50, which effectively modifies the burn rate to maintain the selected conditions at the programmed value.

This programming device 56 is connected to a steam flow request signal supplied through conductor 33 and to a temperature controller 57.
A gas temperature control signal is generated in response to a signal corresponding to the actual gas temperature from the gas temperature control signal. At low steam flow rates, such as those obtained during start-up, the steam temperature at the outlet of the secondary superheater 10 and reheater 11 is substantially equal to the gas temperature at this point. Therefore, as shown in FIG. 2, temperature controller 57 is responsive to the gas temperature at this point. Since gas temperature can only be used as an indicator of steam temperature during start-up and low steam flow conditions, the gas temperature controller 57 is conveniently removable and can be used when the gas temperature is much higher than the superheat or reheat steam temperature. During operation of the device within the normal operating range, the gas temperature controller 5
Remove 7 from the gas duct.

If the gas temperature and, as a function of it, the steam temperature are in a critical state and excessive steam pressure is generated while the combustion is being adjusted to maintain the gas temperature at the programmed value, the steam temperature will be is maintained at the programmed value by flowing through conduit 26 to condenser 12 without passing through superheater sections 20, 10, which is controlled by valve 80 responsive to control signals generated by sequence controller 58.

The invention further provides for controlling the superheated steam temperature by the following means when the critical conditions are the throttle pressure, or the gas temperature or the superheated steam pressure during startup, and the steam temperature during normal on-line operation. including maintaining the desired value. A temperature ramp generator (temperature change rate transmitter) 59 responds to manual setting signals generated within the devices 60, 61, 62 and ramps up to a signal corresponding to an initial desired steam temperature and a desired on-line operating temperature. Generates a signal that increases at an adjustable rate. The initial temperature is typically set to provide the desired temperature difference between the steam and turbine metal temperatures, and the variation ratio is such that the difference between the steam temperature and the turbine metal temperature can be maintained within said limits. are set to increase from the initial to the final value, thus, for example, the initial temperature is 600〓 (315.6°C), the hourly variation rate is 150〓 (83.5C), and the final temperature is 1000〓 (537.8°C).
℃).

The temperature sequence control device 64 is connected to the control device 59
and superheated steam temperature controller 63 to produce an output signal modified by a feed forward signal produced in flow controller 65 responsive to the flow rate of air into furnace 19.
During start-up and low load operation, the output signal from device 64 controls saturated steam detemperature valve 66 to introduce relatively cold air into the superheated steam, thereby restoring the steam temperature to the desired value. . Conversely, if the actual steam temperature decreases below the programmed value during start-up and low load operation, a signal from temperature sequence controller 64, through device 67, adjusts the combustion rate in an upward direction. This control device is such that a signal value corresponding to a decrease in the actual steam temperature below the programmed value adjusts the combustion ratio, whereas a signal value corresponding to an increase in the actual steam temperature above the programmed value adjusts the combustion ratio. A saturated steam detemperature valve 66 adjusts the flow rate of saturated steam supplied to the superheated steam. Furthermore, at the end of low load operation, typically about 20% of full load, the use of saturated steam to control superheated steam temperature is ineffective and valve 66 is placed in the closed position. Thereafter, over the full range of normal load operation, the superheated steam temperature is controlled as required through the feedwater reduction valve 68 in response to signals issued by the temperature sequence controller 64 in response to deviations in the superheated steam temperature from the programmed value. may be controlled by introducing water. (Normally, the final steam temperature is set by a manual device.) Reheat steam temperature control is substantially similar to that described for superheat steam temperature control above. The emitted signal from temperature ramp generator 59 through conductor 68 is transmitted to controller 69 where it is compared with a signal corresponding to the actual reheat steam temperature occurring in temperature controller 70 . In addition, a feedforward signal (a signal that uses disturbance information to perform necessary corrective actions before its influence appears on the control system) is transmitted from the air flow rate controller 65 through a conductor 71 and is transmitted to the reheater temperature. It is introduced into the control device 69.
The output signal generated in the controller 69 is transmitted to the sequence controller 72, which operates the steam detemperature valve 73, the gas recirculation control damper device 74, and the reheat temperature water detemperature control valve 75 in sequence. Similarly, regarding the operation of the superheated steam control auxiliary equipment, the steam desuperheater is
Combustion, which favors the most critical conditions, takes place effectively in certain start-up conditions that produce high reheat temperatures. In the normal operating range, gas recirculation effectively controls the reheat temperature, typically varying against the required rating. At higher ratings,
Gas recirculation is reduced to a minimum and the reheat steam temperature is effectively controlled by water attemperature means.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the basic steam water cycle of the power generation equipment, Figure 2 is a block diagram of the air gas cycle of the boiler shown in Figure 1, and Figure 3 is the diagram shown in Figures 1 and 2. FIG. 2 is a block diagram of the present invention applied to a power generation device. 29... Automatic load transmission system, 30... Primary control signal generator, 32... Load error calibration device, 35... Pressure ramp transmitter, 36, 37, 3
8...Regulator, 42...Steam flow rate control valve, 43...
... Sequence device, 47 ... Pressure control program device, 50 ... Addition device, 52 ... High signal selector, 56 ... Program device, 57 ... Gas temperature controller, 58 ... Sequence control device, 59 ...
... Lamp device, 64 ... Temperature sequence control device, 69 ... Reheat temperature control device, 72 ... Sequence control device.

Claims (1)

[Claims] 1. A control device for a power generation device having a steam generation device 1 and a turbine generator 2 supplied with steam from the steam generation device 1, which generates a feed forward control signal corresponding to a desired output of the power generation device.
a load error correction device 32 that compares the feedforward control signal with an actual output signal and generates a steam flow rate request signal; Turbine steam flow rate control valve 42 that controls the steam flow rate of
a throttle pressure ramp generator 35 that sets a throttle pressure that varies in a functional relationship with the feedforward control signal; and a throttle pressure request signal generated by the throttle pressure ramp generator 35 that is proportional to the actual throttle pressure. a throttle pressure sequencer 43 that issues a control signal to the position valve 46 in response to the throttle pressure request signal and a signal proportional to the actual primary superheater outlet pressure issued from the pressure controller 48; Boiler pressure program controller 4 responsively issuing an output signal
7, a program device 56 that receives a steam flow rate request signal sent by the load error correction device 32 and an actual gas temperature signal sent by the gas temperature controller 57, and sends out a gas temperature control signal; and a position valve 46 that sends a throttle pressure control signal. If the requirements of the boiler pressure program controller 47 cannot be satisfied, the signals transmitted from the sequence control device 58 which receives the signals transmitted by the boiler pressure program controller 47, the signals transmitted from the program device 56, and the signals transmitted from the throttle pressure sequence device 43 are transmitted. a high signal selector 52 that receives the signals and transmits the best of those signals;
and an addition device 50 that controls the fuel flow control valve 40 and the air flow control damper device 41 in response to the signal transmitted from the high signal selector 52 and the steam flow rate request signal transmitted from the load error correction device 32. A control device for a power generation device, characterized in that: