JPS5941605A - Two-boiler type turbine type power generating apparatus control system - 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 This invention relates to an integrated control scheme for large scale power generation plants such as those found in modern central stations. In order of magnitude, such a device may e.g.
10100 requiring 0.00000 lbs. or more of main steam
The estimate could be higher than O. Customarily, in such systems, steam is first passed through a high pressure turbine and then passed through a reheater line in the steam generator which raises the steam to a hot reheat temperature of approximately 100 OIP, and then It passes through a low-pressure turbine to a condenser.

To improve the reliability of such power plants and to keep the steam generator dimensions reasonable, plants have recently been equipped with two steam generators operating in parallel to meet the total steam demand of the turbine. It has been proposed to do so. Such a combination of two steam generators and a single turbine generator presents unique control problems, as will be apparent from the detailed description below. The purpose of this invention is to solve these problems.

However, it will be appreciated that the novel control scheme of this invention has features that are equally applicable to many conventional single turbine generator/single steam generator configurations.

According to the invention, the total output of the two steam generators is maintained primarily in accordance with the unit MW or energy factor as established by an automatic load command or other device.

Furthermore, according to the invention, system energy requirements can be distributed between two steam generators as needed.

Additionally, the present invention allows, for example, if the output of one steam generator is limited, the output of the other steam generator is automatically increased to meet the system energy requirements.

In accordance with the present invention, if the total available power of the two steam generators is insufficient to meet the system energy demand, the demand is reduced to match the total available power. .

Broadly speaking, in accordance with the present invention, feed water, fuel and air are supplied to each steam generator primarily in accordance with the magnitude of the equipment energy requirement assigned to the steam generator.

In addition, according to the invention, the total reheated steam flow from the turbine is distributed between the two steam generators according to the distribution of the equipment energy requirements, which are mainly distributed between the two steam generators. .

These and other objects of the invention will become apparent from the following description of the accompanying drawings.

Now, referring to Figure 1, it is called a normal boiler.

Steam generator %-A, E and a common turbine-generator arrangement with a high-pressure turbine 9 and a low-pressure turbine IO The water cycle is shown.

As shown, both the high-pressure turbine and the low-pressure turbine can drive a single power generator, or each turbine can be a separate power generator feeding a common bus. :4f? can be driven.

The specific construction of the turbine and generator that may be used does not form part of this invention. Each steam generator'
:The steam released from the sub-superheating devices/, 2A, /IB of A and B passes through the high pressure turbine and is divided, and a part of it is reheated by the reheating device/, ? A, the remaining part is sent to the reheating device 13B.
pass through. And the hot reheat steam from reheat units i, ih, laB connects low pressure turbine io ab and condenser fl
It is released into Dahe. What is shown as a low pressure turbine may actually be an intermediate pressure turbine and one or more low pressure turbines.

The condensate from the condenser unit lt is fed by the condensate pump is to the low pressure U heat unit/&A, heated by extracted steam from the low pressure turbine IO to the air separation heating unit/&A, and also from the low pressure turbine 10. It is also heated by the extraction steam. Water is supplied to boiler A through heating device 1 for air separation.
7 by the boiler feed water pump/gA, and is supplied to the furnace 20 through the high-pressure heating device/9k and to the boiler A equipped with a main superheater co/A and an auxiliary superheater/coa. The water supply to boiler B is also drawn out from the air separation heating device/2 by the boiler feed water pump/gB, and then passes through the high pressure heating device/9B to the furnace B, main superheating device B, and sub superheating device/2B. It is supplied to boiler B, which is equipped with

Figures JA and -B show the air/gas cycles for boilers A and B, respectively. These cycles are identical, and for brevity only the cycle for boiler A will be described. Components of boiler A in FIGS. 2A and 2A are designated with a letter in addition to the number, and similar components of boiler B in FIG. 2B are designated with the same number followed by the letter B.

Referring to FIG. 2A, the combustion air supplied by forced draft fan 2.2 is air 711'I thermal device, 23
It passes through A and is supplied to furnace-〇A. The fuel, which may be oil, gas, coal or a combination of the following, may be any conventional fuel supply device (not shown, but abbreviated by line 24).
is supplied into the furnace 20A. Combustion gas, usually called flue gas, coming out of the furnace is released into the atmosphere through a chimney (not shown). Roaring section-/A, air heating device, 23
A and suction fan, i! Pass through 5A. Main overheating device! The flue gas exiting from 2/A is also reheated as a foil to partially or totally control the reheat steam temperature.
Recirculated into the furnace-OA by the current fan roller A9
Ru. Generally, the flow of recirculated gas S is maintained inversely proportional to the heat- or energy input to the boiler. Combustion g q'
The illustrated order in which p, t passes through several heating sections is not an exclusive order. For example, this order is
The order may be a superheating device and a reheating device, or a subheating device, a main superheating device, and a reheating device. Similarly,
Saving devices can also be provided at appropriate locations.

FIG. 3 shows the configuration of the control system in a block diagram. A charge request may be established by an automatic load command device-g or other automatic or manual device.

The purpose of this control is to generate a control signal commensurate with the desired energy output, which may be measured in MY, BTU, or other energy units. The control signals thus generated are transmitted to a master controller 30, which can be any one of a number of types generally common in the art. The model suitable for one size is Babcock &
It is illustrated and described in "stθam" 3rd edition, Chapter 35, published by Wilcox. The purpose of the main controller is to generate a control signal for the steam generator from the control signal generated by the load controller-g, thereby maintaining the actual energy output of the generator equal to the desired energy output. .

The control signals generated in the main controller 30 are transmitted to the ratio controller 32, which ratio controller 3.1! The operation is within the range of the generator's performance as required.

The purpose is to distribute the total load demand between the steam generators A and B in a single step. That is, this ratio system 1 device divides the control signal from the main controller 30 to form a first request signal for boiler A and a second request signal for boiler B. The first request signal is sent to the water supply control device 3 of boiler A as shown in the figure.
fA and ignition rate control device 341. The two request signals F′i generated in the ratio controller 3.2 are also transmitted to the reheat flow controllers + and 2, and the function of this reheat flow controller 112 is to control the boilers A and B according to the boiler load. The purpose is to distribute the reheat steam flow.

Figures q, s, t, and 7 show the ratio, water supply, ignition ratio, and reheat flow control device for boilers A and B. It can be seen that conventional control logic symbols are used in these figures. Control components, often referred to as hardware, with various symbols are commercially available and their operation is well understood by those skilled in the art. moreover,
Since the invention can be combined with any special type of control device such as pneumatic control, fluid control, electronic control, electric control or a combination thereof, a control scheme with such a special type of control device may be used. Use conventional logical symbols to avoid checking. $；q.

! , A, the main controller shown in FIG. 7 is the first, . 2A, 2B
It has been referred to as the final control element in the figures.

Referring to FIG. 7, the control signal corresponding to the total boiler demand generated by the main controller 30 (FIG. 23) is sent to the multiplier Dada, from which the output signal is transmitted to the multiplier [
Sent to 44. The portion of the total boiler demand to be scheduled for each boiler is formed by the ratio controller g.
generates a control signal, which is transmitted to the multiplier IIl.

Therefore, the output signal from the multiplier φ is the desired signal for the seboiler A. Difference device 11. In Party B, boiler A
The request signal of is subtracted from the total boiler request signal or n1 difference device 1
The output signal from l-6 is the boiler B request signal.

If one or more factors in the operation of boiler A or boiler B are limited to or above a predetermined limit, it is necessary to limit the demand signal to the boiler accordingly.

Factors limiting boiler output by supply represent fuel flow, air flow, feed water flow, reheat flow and superheat flow during bypass operation. The factor that limits the boiler output when the predetermined limit is exceeded represents the furnace draft, which can exceed the predetermined positive limit if the performance of the draft blower is limited.

The factors mentioned above will be considered to be merely representative of the many factors that can impose limits on boiler performance.

As shown in FIG. 7, such a factor is considered to be a criticality generation signal that forms an input to limit controller Dub A of boiler A and a similar limit controller Q9B of boiler B.

Departures in the dead band (dθadband) of less than 5 inches are ignored to avoid momentary small departures beyond the scheduled limits that unnecessarily stress boiler demand.

However, if the sustained departure is greater than 5%, the deadband error signal is reduced to 1%, so that only errors less than /% are ignored.

The demand signal for the boiler is therefore returned to match the forced boiler capacity. Limit control equipment guwa A, gu9
The output signals from B are integrated with respect to time in the three Bs, respectively into an integrator, 3.2, and each with a low i
It is sent to selector Sth and JAB. Therefore, the signal from multiplier Dada or the signal from integrator 52A, whichever is smaller, is the actual demand signal for boiler A.

Similarly, the signal from the difference device 6 or the integrator 3.2B
The smaller of the signals from is the actual request signal for boiler B.

Even if the output of one boiler is stressed, it is desirable that the total output of the two boilers should meet the unit energy requirement. Therefore, the present invention encompasses the case where the output of one boiler is limited and the output of the other boiler is automatically compensated by increasing the output. For this, the output signal of the difference device 60Af'i multiplier device lIq and the low signal selector St.

A signal is generated that is proportional to the difference between the output signal of A and this signal is sent to the summation device 6g through the direct proportional compensation device 6.Similarly, the difference device bOB generates a signal proportional to the difference between the output signal of the difference devices and the low signal. A signal proportional to the difference between the output signal and the output signal of the signal selector JAH is generated, and this signal passes through the inverse proportion device 66 to the total sum device 6g.
sent to.

If both boilers A, B carry the loads assigned to them, i.e. neither output is limited, the output signal generated by the summing device 6g is zero. If the output of boiler A is limited, the summation device 6
The output signal from g operates the transmission device 70 and thereafter serves as the input signal for the multiplier t. Since the output signal from the multiplier 1I changes to be equal to the output signal from the integrator S, the demand signal for the boiler B is correspondingly increased by the operation of the difference device 6.

Squeezing at the output of boiler B operates in the same way, the output signal from the inverse proportional device A6 being passed through the summing device 6g and the switching device 0 to the demand signal for boiler A until the output signal from the difference device AOB is zero. and boiler B
This acts to reduce the request signal for.

If, after a scheduled time of ~5 minutes, the load changeover from one boiler to the other cannot be made to satisfy the total boiler demand, the unit load demand will be equal to the actual performance of the two boilers. will be reduced to Difference device AOk
The unsatisfied demand at boiler A, represented by a sustained output signal from Returning to the requirements, the overall performance of the two boilers is matched. An output signal representing a sustained unsatisfied demand on boiler B is also sent to device 7.2 from difference device bOB.

Obviously, the high signal selector 72 is the device load command device-g.
Different device AOA.

It acts to pass the larger of the two error signals generated at 60B. Therefore, for the difference device B θ, AOB
If the greater of the two signals representing an unsatisfactory demand in either boiler from either boiler is reduced to zero by a return to equipment load demand, then the unsatisfied demand in both boilers is reduced to zero. .

In a typical single-boiler, single-turbine configuration, the feed water temperature varies with a directly predictable function of equipment load. In a double boiler-turbine configuration, as in the case of the present invention, the two boilers operate at the same load for as long as possible. However, this relationship is broken whenever the two boilers operate at different loads since the feed water temperature is a function of the turbine load. The relationship between the feedwater temperature and the actual steam flow entering the turbine, which is equal to the total feedwater flow to both boilers, is directly related to the total turbine extraction flow to the high pressure, low pressure air separation feedwater heating system. Therefore, a feedwater temperature that is lower than that expected for the existing boiler demand is directly related to the existing low steam flow to the turbine which is equal to the low required boiler feedwater flow. Therefore, if the feedwater temperature is higher than that expected for the existing boiler demand, the feedwater demand is increased to result in an actual increase in steam flow to the turbine resulting from the increased extraction flow.

In the control system shown in Figure S, the flow rate of feed water to each boiler is maintained in direct proportion to boiler demand. Therefore, the control signal generated in the three ratio controllers is the feedwater control valve 74'.
Sent to A. A feedback loop comprising the flow transfer device 7AA, the difference device 7gk, the integrator gOA and the multiplier device g2 maintains the actual feed water flow equal to the requested feed water flow.

In order to provide for the departure of the actual feedwater temperature from the temperature expected for the existing boiler demand, a signal corresponding to the expected feedwater temperature generated from the function generator g3A is transmitted in the differential device gAk to the temperature transfer device gtA. is compared with a signal corresponding to the actual feed water temperature generated by The output signal from the difference device g6A is passed through the summing device ggh to the multiplier g7 to modify the demand control signal according to the deviation of the actual feed water temperature from the expected temperature for the existing boiler demand. .

Also, the desired feedwater flow rate for a given boiler demand is affected by changes that may occur in the steam temperature set point from the normal or design set point. Therefore, increasing the desired steam temperature from the normal temperature will reduce the feedwater flow rate and vice versa. Control signals corresponding to changes in the steam temperature set point generated in device 90 AVC are sent to the summation device ggh.
The desired compensation is achieved by changing the output of

Although the water supply control device for boiler B has been illustrated and described above, it should be understood that the water supply control device for boiler B is the same as that for boiler A in all respects.

The demand signals for boilers A, B adjust the required boiler heat release to meet the required energy output of the power plant. Heat release is directly related to the fuel BTU input to the boiler's furnace. The boiler demand signal thus regulates fuel flow at the same time as air flow. It is observed that the required combustion air flow for a given fuel and fuel BTU input remains essentially constant. The present invention directly matches airflow to boiler demand because the boiler demand signal is directly equated with the required energy output and because the overall cycle efficiency at each load is relatively constant and predictable. Fuel flow is readjusted as necessary to maintain the two boiler superheater outlet temperatures equal and at the turbine throttle temperature set point.

As shown in FIG. 6, in accordance with the above description, the demand signal for boiler A is determined by the final control element, such as the Dan A drive, which controls the flow rate of air supplied for combustion. /A. A feedback signal from the flow transmitting device 9.2 proportional to the measured airflow maintains the actual airflow equal to the desired airflow. The signal generated in the transmission device 9.2 is sent to the difference device 3A, and the output signal is passed through the proportional-integral device 132A to adjust the airflow damper 9/A as necessary to adjust the actual airflow. acts to maintain the airflow equal to the desired airflow.

A signal proportional to the temperature error from the set point and the rate of change of the superheater outlet temperature of boiler A is superimposed on the demand signal in a direction opposite to the direction of temperature change, thereby reducing the instantaneous fluctuations in the superheater outlet temperature. Compensate for. As shown,
A signal corresponding to the temperature at the outlet of the superheater is sent to the temperature transfer device 4t.
generated in A, and proportional/differential 75 q3
A and thus transmitted to the summation device 9A.

Boiler A modified according to the rate of change of superheater outlet temperature
(jH also controls the fuel flow rate to maintain the Ayuhiro flow rate in the required relationship to the air flow rate. As shown, the output signal from the summation device 96A is connected to the fuel control valve The carving end fI shown in Figure 18 as
111 element 97A, the special type of explosive 9 flow control device used relates to the fuel citron. Suspension flow transmission device 9
A feedback loop with gA, the input %"9?A, and the proportional-integral Hiooh maintains the actual flow rate of the cooking material equal to the requested flow rate of the furnace charge.

Due to a relatively long-term change in the turbine throttling rate, which represents a change in the BTU content of fuel f1, for example, the ratio of air flow to furnace feed flow changes, and thus the actual free to air flow rate changes. Automatically and continuously adjust the flow rate. Kof
This is achieved by introducing the signal generated in the turbine throttle temperature transfer device lθ3 into the integrator 10/A, and the output signal from the integrator IO/A is multiplied by 38?
-Solution @ / 0, i! Sent to A. Thus, the output signal from the multiplier 10A is determined in accordance with the long-term change in the turbine throttle temperature, which is inferentially a measure of the change in the relationship between the heat input to the boiler and the flow rate of the fuel flow transfer device 9G.
Works to change feedback signals from people.

The ignition rate control device explained above has been specified for controlling boiler A, but as can be seen from Fig. 6, the control device for boiler B is also the same, and the same constituent elements have the same number with the letter B. shown below.

In order to avoid the interaction commonly referred to as hunting between the superheater outlet temperatures of the two boilers while maintaining the desired turbine throttling temperature, a push-pull control device is additionally shown; Thereby the fuel flow to the boiler with a relatively high superheater outlet temperature is reduced and at the same time the fuel flow to the other boiler if L
/i is increased, thus maintaining the superheater outlet temperature equal while simultaneously adjusting the flow of fuel to both boilers according to variations in the throttling steam temperature from the set point. As shown, a signal proportional to the difference between the superheater outlet temperatures of boiler A and boiler B is generated in the difference device/coin;
and a direct acting proportional device L-da and a floating proportional device JIt,
It is sent to the integrated circuit 10S), , 103B via the 1 controller 5, and the input signal to the f1 integrator 10IA, 10/B is biased in the opposite direction.

This invention balances the reheat steam from the high-pressure turbine between boilers A and B according to the forward feed s derived from the request signal for each boiler, and at the same time makes the reheat flow to each boiler proportional to the main steam generation. Includes maintaining. In FIG. 7, the demand signal for boiler A positions the final control element, flow control valve 1oth. Similarly, a demand signal for boiler B positions flow control valve 107B. By means of the function generators iogh, iogB, any desired linear or non-linear functional relationship between the reheat flow and the demand signal for boilers A, B, respectively, can be programmed. Proper distribution of the total available reheat flow is obtained by a push-pull feedback control loop, thereby maintaining equal differences between the actual and programmed reheat flows through each boiler. As shown, the reheat flow through boiler A and boiler B is channeled through flow transfer devices lOWA, 10? Measured by B.

Although the main elements of the reheat flow have been schematically shown as orifices in FIG. 1 for simplicity, the present invention uses arbitrary pressure drops that vary in a functional relationship to the flow to minimize unrecovered pressure losses. A pressure drop through a reheating device may be utilized or a main element such as a Venturi tube or a single nozzle may be utilized. Known flow measurement devices other than those that generate differential pressures that vary with flow may also be used. Additionally, as is well known, the pressure and temperature of the reheat stream, which varies with the reheat stream and the flow transfer device, can be compensated for both of these conditions by any suitable device.

The difference between the actual reheat flow and the programmed reheat flow through each boiler is determined by the difference device/lθ, l10H. As an example, the actual reheat flow which is larger than the programmed reheat flow may be different from the device t:i, / / OA or / 10
It can be thought of as generating a positive output signal from B. The generated signal is sent to the difference device: / / /. The output signals generated here are proportional-integral device l/, 2 and commuting and direct-acting proportional device @//3A.

//3B and Sogo Sosobu //HiroA respectively.

//'Supplied to IB. Total loading%l//daA.

The output signal from /I'lB is therefore reversed to IO'lB to the reverse positioning valve 107 to maintain the difference between the actual and programmed reheat flows equal. Obviously, the allowed adjustment 1 may be limited to maintain equal differences if necessary.

As mentioned above, by suitable distribution of the total reheat flow between the two boilers, the desired reheat temperature Vi can be obtained by gas recirculation as shown in FIG. may be supplemented by atomizing means or other known devices. However, if the hot reheat temperature of a boiler exceeds the set point, the invention increases the reheat flow to that boiler while decreasing the reheat flow to the other boiler, and the hot reheat temperature of both boilers exceeds the set point. Exceeding the point involves increasing the ladle heat flow to the larger boiler while simultaneously decreasing the reheat flow through the other boiler.

This action therefore maintains the excess hot reheat temperatures from both boilers equal.

Temperature transfer device /ISA, /15B is boiler A.

A signal corresponding to the hot reheat temperature of B is generated. These signals are passed to the high signal selection device 111. A, /11. B is compared against the setpoint signal. As long as the signal generated in the transmission device R/15k is, for example, below the set point, the device //1, A sends the set point signal to the differential device //7. However, when the corresponding signal of hot reheat temperature exceeds the set point signal, it is sent to the differential device //7. At the same time, as long as the signal generated by transmission device /15B is below the set point, the signal sent to differential device /15B is the set point signal. However, if the signal generated in the transfer device //SB is greater than the set point signal, then that signal is sent to the differential device P7. As is clear from the above description, the output signal from the differential device //l has a neutral value such as zero as long as both hot reheat temperatures are at or below the set point.

However, if the hot reheat temperature of one boiler exceeds the set point, the device //7 will generate a one-way signal, and if the hot reheat temperature of the other boiler exceeds the set point, the device //7 will generate a one-way signal.
7 generates a signal in the opposite direction.

Assuming that the hot reheat temperatures of both boilers exceed the set point, the device l/l is adjusted in the direction associated with the boiler with a higher hot reheat temperature and a value commensurate with the difference between the two hot reheat temperatures. Generates an output signal.

The signal generated in the difference device l/ri is transferred to the linear proportional device l/ri.
A and a floating proportional device 1/gB. These devices act to change the forward synchronization signals for boilers A and B in the opposite direction via the summation devices θA and /OB, and thus reverse the positioning of the valves 107k and 107B. and maintain the hot reheat temperatures from both boilers below the set point, and equally maintain the hot reheat temperatures from both boilers when both such temperatures are above the set point.

When reheat attenuators are rarely used and the reheater absorption and loading characteristics are such that the two boilers are often operated with unbalanced steam flows and therefore unbalanced reheater exit temperatures. Another construction that is particularly applicable is to improve reheater temperature control performance by biasing the steam flow through the reheater whenever a temperature difference below or above a set point exists at the outlet of the two reheaters. It is about maintaining. To accomplish this, the high signal selection device //bA, //AB difference device //7 forms the reheater exit temperature error from the set point for comparison in the differential device//7 as shown in FIG. 7A. 30 is replaced with l30H. Whenever either reheater exit temperature error differs from a comparable error from the other boiler, reheat steam flow is increased through the reheater with a higher exit temperature.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the basic steam-water flow cycle of a typical power generation device having two single reheat steam generators that supply steam to the turbine; Figure 2A is a block diagram showing the steam generator A shown in Figure 1; Block diagram showing the basic air/gas flow cycle of, part,! Figure B is a block diagram showing the basic air/gas flow cycle of steam generator B shown in Figure 1, Figure 3 is a block diagram showing the configuration of the control system, and Figure D is a block diagram showing the block 32 for the third factor. A logic diagram showing details of the ratio control device shown in FIG. 5, block 34! -A, J4'B
A logical diagram showing in detail the feed water flow control device for each of the steam generators &: A and E shown in FIG. 6 #-j: Block 31. , A, 31. A logical diagram showing in detail the ignition rate control device (fuel and air control device) for each of the steam generators A and B, respectively indicated by B, and FIG. 7 is a reheat steam control device shown in the block diagram in FIG. 3. FIG. 7A is a basic logic diagram showing a modification of the reheat steam control device shown in FIG. 7. In the drawing, -g is the negative command device, 3o is the main control device, 3 is the ratio control device, 3 Hiro A and 3 Hiro B are the water supply flow control device, 3
1. A, 3ABFi ignition rate control device, 4t2Vi, reheat flow control device. Procedural Amendment (Method) July 29, 1980 Mr. Commissioner of the Patent Office 1. Indication of Case 1988 Patent Application No. 122490 2. Name of Invention Nizeira - Control Method for Turbine Type Generator 3. Amendments to be made. Patent Applicant 4, Agent 105 Address Bussan Building Annex, 1-15 Nishi-Shinbashi, Minato-ku, Tokyo Telephone (591) 0261■, Specification 2, Drawing 6, Contents of Amendment 1 :) Another 2 As per the paper

Claims (1)

[Claims] l A boiler A that supplies steam to a single turbine in parallel;
a device that generates a request signal for boiler A; a device that generates a request signal for boiler B; a device that maintains the fuel supply amount to boiler B in a functional relationship with the boiler B request signal in response to the request signal of boiler B; and a device that maintains the fuel supply amount to boiler B in a functional relationship with the boiler B request signal; A control system for a power generation plant comprising a device for changing the functional relationship between the turbine throttle and the steam temperature according to the integral over time of the variation from the set point of the steam temperature. U. Boiler A that supplies steam to the high pressure section of the turbine and reheated steam to the low pressure section of the turbine, and the boiler A above.
and a boiler B that supplies steam to the high pressure section of the turbine and reheated steam to the low pressure section of the turbine in parallel with the system, and includes a device that generates a request signal for boiler A and a device that generates a request signal for boiler B. a device for changing the flow rate of reheated steam passing through boiler A in response to a demand signal from boiler A in a functional relationship with respect to a change in the demand signal for boiler A; A control system for a power generation device which is combined with a device that changes the flow rate of reheated steam passing through boiler B in a functional relationship with respect to changes in the request signal of boiler B.