US3925645A - System and method for transferring between boiler-turbine plant control modes - Google Patents

System and method for transferring between boiler-turbine plant control modes Download PDF

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US3925645A
US3925645A US556363A US55636375A US3925645A US 3925645 A US3925645 A US 3925645A US 556363 A US556363 A US 556363A US 55636375 A US55636375 A US 55636375A US 3925645 A US3925645 A US 3925645A
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signal
transfer
boiler
turbine
value
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US556363A
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Louis P Stern
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Westinghouse Electric Corp
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Westinghouse Electric Corp
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Priority to FR7606141A priority patent/FR2303157A1/fr
Priority to BE1007229A priority patent/BE839221A/xx
Priority to IT20904/76A priority patent/IT1056907B/it
Priority to JP51023351A priority patent/JPS5917242B2/ja
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B35/00—Control systems for steam boilers
    • F22B35/18—Applications of computers to steam-boiler control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K13/00—General layout or general methods of operation of complete plants
    • F01K13/02—Controlling, e.g. stopping or starting

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  • ABSTRACT A boiler-steam turbine plant control system for trans- CPB J- PLANT MODE TRANSFER CIRCUITRY ferring between boiler-follow, turbine-follow, and coordinated operating modes, without any change in the output of the turbine or the firing rate of the boiler, is disclosed.
  • a feedforward load demand signal controls both the turbine and boiler in parallel.
  • a feedback loop trims the feedforward signal to the turbine only.
  • a feedback loop trims the feedforward signal to the boiler only.
  • feedback loops trim the feedforward signal to-both the turbine and boiler.
  • the load demand signals which are controlling the boiler and turbine are held at their pre-transfer value; and the feedforward signal is modified to equal the pre-transfer value of the trimmed feedforward signal.
  • 'A signal which is equal in value to the pre-transfer value of the feedforward signal less the value of the trimmed feedforward signal is generated in the output of the feedback loop which is to be placed in service as a result of the transfer.
  • the feedforward signal is modified to equal a signal representative of the actual power output of the plant.
  • the turbine feedback loop generates a signal representative of the pre-transfer turbine demand signal less the modified feedforward signal.
  • the boiler feedback loop generates a signal representative of the pro-transfer boiler demand signal less the modified feedforward signal.
  • FIG.7 ANALOG OUTPUT A J'A'A' M RAISE INHIBIT LOWER INHIBW 37 DN up F
  • D/A CONVERTER 152 AUTO 100% o o A OUTPUT OUTPUT O V o MAN 0 SYSTEM ANDMEIHQD FOR T ANSEER I G BETWEEN BOILER-TURBINE PLANT CONTROL PE I' BACKGROUND OF THE INVENTION
  • the present invention relates tocontrol systems for power plants; and more particularly to a system for transferring rapidly between operating modes without a change in the output of the turbine or' the firing rate of r the boiler.
  • control is achieved by a plant master control unit or load demand computer, whichgenerates a feedforward load demand signal that is connected in parallel to a turbine master control apparatus for operating the steam inlet valves to a predetermined position in accordancewith the valve of the feedforward signal, and to a boiler master control apparatus for controlling the fuel, air, and water to the boiler at a predetermined rate in accordance with the value of the feedforward signal.
  • the feedforward demand signal from the load demand computer minimizes interaction between the turbine and boiler, and extracts the best possible dynamic response ofthe plant.
  • the load demand signal to the turbine and the boiler master control is trimmed by an error signal from an analog feedbackloop, in response to detection of throttle pressure error and megawatt pressure error.
  • the measured throttle pressure is compared to a reference level determined by a set point to pro vide the throttle pressure error signaLwhich is integrated and applied to the turbine control.
  • the output'of the turbine is measured and compared with a reference to provide megawatt error, which is integrated and applied to the boiler control.
  • a typical modern plant 'control system provides for several different modes of operation for various plant conditions.
  • a throttle pressure error feedback loop and a megawatt error feedback loop is in service.
  • One feedback loop trims .the load demand signal to the boiler control with the megawatt error signal; and the other feedback loop trims the turbine load demand signal to the turbine control with the throttle pressure errorsignali
  • an increasing load demand results in the throttle pressure and megawatt generation to be' low.
  • the .throttle pressure set point is increased by an amount proportional to generator error; and atthe same time the firing rate of the boiler is increased, the'throttle pressure is lowered momentarilyas the governor valves are opened to permit greater steam flow.
  • the system can be transferred either automatically or manually to either a boiler-follow or a turbine-follow mode.
  • the system is transferred to the boiler-follow mode wherein the feedforward signal from the plant unit master or load dewherein the feedforward signal sets the boiler to operate according to predetermined limits, and the feedforward signal is trimmed by the turbine feedback loop to adjust the governor valves to maintain a substantially constant pressure.
  • the present invention relates to a system and method of transferring from one plant control mode to anotherin a boiler-steam turbine power plant wherein a feedforward signal representative of the desired plant load is generated to control in parallel the boiler portion of the plantand the steam turbine portion of the plant in each of the modes.
  • the trimmed and untrimmed load control signals to both the boiler and the turbine are held at their pre-transfer value in response to the initiation of a transfer.
  • the feedforward signal is modified to represent a selected value depending on the operating mode being entered. If one of the control apparatus is to be operated with no feedback loop in service, the selected value is the pre-transfer value 'of its trimmed input.
  • a feedback signal is generated so that the input signal to its respective boiler and turbine control apparatus is representative of the boiler and turbine control apparatus input signal which is held at its pre-transfer value.
  • the boiler and master control are permitted to respond to their respective trimmed and untrimmed signals in the transferred mode.
  • the system includes a load demand computer which generates feedforward signalsin parallel to the turbine and boiler control apparatus.
  • a feedback loop is provided for the turbine control apparatus which trims the feedforward signal tocorrect for any deviation in throttle pressure.
  • a feedback loop is provided for the boiler control apparatus to correct for any deviation in throttle pressure; and a feedback loop is provided for the boiler control apparatus which operates in conjunctionwith the feedback loop for the turbine control apparatus to correct for throttle pressure and megawatt error.
  • Each one of the feedback loops includes a proportional plus integral controller, and its error signal is summed with the feedforward signal to provide the trimmed signal.
  • a manual/automatic transfer device for each master control apparatus receives the signal from the summing device and generates a signal corresponding to the summed signal for its associated master control.
  • each manual/automatic station In response to the initiation of a transfena digital pulse of predetermined duration is generated, which governs each manual/automatic station to holdits output signal at its pre-transfer value.
  • the feedforward signal to each of the summing devices is modified to be representative of a selected pre-transfer value, which selected value for a transfer where a particular control apparatus will have no feedback loop in service is the pre-transfer value of the output of the manual/automatic station for such control apparatus.
  • the feedback controller is governed to generate an output signal for input to each summing device representative of the pre-transfer value of the output of the manual- /automatic transfer station less the modified feedfor ward signal to the summing device.
  • the feedforward signal is modified to be representative of the actual megawatt output of the plant.
  • the turbine 4 or boiler feedback loops are each operated to generate a signal which isrepresentative of the pre-transfer output of its manual/automatic station less the modified feedforward signal.
  • the outputs of the feedback loops are summed with the modified feedforward signal.
  • the hold on the output signal of both manual/automatic stations is released, and the feedback controller for the connected loop is permitted to change its signal to the summing device in accordance with the error between the actual pressure or megawatts and the set point as the case may be,
  • FIG. 5 is a schematic diagram of one form of a proportional plus integral feedback controller for use in the system of the invention.
  • FIG. 6 is a schematic diagram of one fonn of a summing device for use in the system of the invention.
  • FIG. 7 is a schematic diagram of one form of a difference function device foruse in the system of the invention.
  • FIG. 8 is a schematic diagram of one form of a manual/automatic station for use in the system of the invention.
  • FIG. 9 is a schematic diagram of one form of a mode select logic circuit for use in the system of the invention.
  • FIG. 1 there is shown schematically a general block diagram of an analog 'plant control system wherein analog feedback error signals are selectively connected to be summed with a feedforward signal for operating the turbine and boiler control in accordance with a selected plant operating mode; and includes a block diagram of a system for transferring between such operating modes with a change in the position of the turbine inlet valves, boiler firing rate, or the megawatt output of the turbine.
  • a load demand computer 10 which is shown in detail in FIG. 3 generates a load demand signal on output 11 to the input of summing devices 12 and 13, the details of which are shown in FIG. 6.
  • the load demand computer 10 may be any signal generating device which functions as disclosed, and is constructed to generate a feedforward signal, the value of which is calculated to correspond to a desired load for the plant.
  • a mode select pushbutton BPB is operated toplace the plant in a boiler-follow mode; a mode select pushbutton TPB is operated to place the plant in a turbine-follow mode; and a pushbutton CPB is operated to place the plant in a coordinated mode.
  • logic circuitry described in connection with plant mode transfer circuitry 28 is employed to energize selected ones of the outputs 14, 15 and 16, for
  • relay contacts 17, 18 and 19 opening or closing respective relay contacts 17, 18 and 19, to connect and disconnect outputs 20, 21 and 22 of feedback controllers 23, 24 and 25, for input to the associated summing devices 12 and 13.
  • conventional relays and contacts are shown for the sake of simplicity, it is understood that other type switching circuits may be used.
  • the load demand computer may also include a device 26 for increasing or decreasing manually the value of the analog signal on its output -11. This, of course, in an actual planemay be also accomplished automatically.
  • the load demand computer 10 also includes an input 27, which, when energized by a digital signal from the transfer circuitry 28, the details of which are shown in FIG. 2, functions to modify the feedforward signal on the output 11 to be equal to an analog signal on input 30 from the transfer circuitry 28; or in other words the load demand computer 10 tracks the value of the signal on the input 30, when the input 27 is energized.
  • the feedforward signal on the output 11 of the load demand computer 10 is connected in parallel to a turbine master control 33 and to a boiler master control 36.
  • the signal to the summing device 12, is conducted by way of output line 31 to the manual/automatic station 32; for input to the turbine master control mechanism 33.
  • the signal on the output 11, which is input to the summing device 13, is conducted by output 34 to a manual/automatic station 35 for input to the boiler master control 36.
  • the analog summing devices 12 and 13 may be of the type shown in FIG. 6, or any well known device that functions as described herein.
  • the manual/automatic stations 32 and 35 may be of the type shown in detail in FIG. 8, which function to either increase or decrease the value of an analog signal manually or automatically.
  • Each of the manual/automatic stations 32 and 35 also function to prevent the manuallautomatic stations 32 and 35, when in automatic, from responding to a change in the value of a signal on their input lines 31 and 34 at times when a digital signal is present on output 37 of the transfer circuitry 28. In other words, the presence of a signal on line 37 prevents a change in the value of the signal on line 38 to the turbine control mechanism 33, and on line 40 to the boiler control mechanism 36.
  • the turbine master control 33 may be of the type that is well known in the art, and includes all apparatus necessary to position the steam inlet valves to the required position in accordance with the value of the signal on its input 38.
  • the boiler master control 36 also may be of any well-known type that functions to adjust the fuel air and feedwater of the boiler to control its firing rate in accordance with the value on the input signal 40.
  • the feedback controllers 23, 24 and 25 provide the output error signals for input to the summers 12 and 13 depending upon the particular control mode in which the system is operated.
  • Each of the controllers is a proportional plus integral type controller which produces at its respective output 20, 21 an error signal, which trims the feedforward signal on output 11, for more accurately controlling the turbine and boiler master control mechanism 33 and 36.
  • a device TP for detecting the actual throttle pressure of the plant during operation, and a set point input SP for applying to its controller the desired throttle pressure. The signal from TP is compared with the set point signal from SP to determine the value of the error signal at the output of its associated controller 23 and 24.
  • the feedback controller 25 detects the actual megawatt output from the turbine by a detector MW, which is compared mm the feedforward signal on the output 11 of the loaddemand computer 10 to provide an error signal on output 22, which corresponds to the difference between the desired megawatt output and the actual megawatt output of the plant.
  • the feedback controllers 23, 24 and 25 also include respective analog inputs 41, 42 and 43, and respective digital inputs 44, 45 and 46 from the plant load transfer circuitry 28. Each of the controllers function to generate at their respective outputs 20, 21 and 22, a signal representative of the analog signal on the associated inputs 41, 42 and 43 at times when a digital signal is present on the respective inputs 44, 45 or 46 from the plant load transfer circuitry 28.
  • the associated feedback controller in response to a digital signal on lines 44, 45 and 46, which may be termed track enable inputs, the associated feedback controller conducts an analog signal on its respective output 20, 21, 22, which is representative of the value of the analog signal on its associated input 41, 42 and 43.
  • This function may be referred to as the feedback controller tracking a particular analog signal; and the purpose of which is discussed in detail in connection with the description of FIG. 2.
  • the feedback controller 23 When the plant is in the turbine-follow mode, the feedback controller 23 is connected to the summing device 12 through the closed contact 17, and the feedback controllers 24 and 25 are disconnected from the summing device 13 because of the open condition of the contacts 18 and 19.
  • the feedforward signal on the output 11 of the load computer 10 governs the boiler master control without correction; while any difference between the actual throttle pressure and the throttle pressure set point is corrected by the error signal on the output 20 of the feedback controller 23, which is summed with the feedforward signal on the output 11 by the summing device 12.
  • the output of the summing device 12 conducts the corrected or trimmed feedforward signal by way of output 31, to the manual- /automatic station 32, which in turn applies such signal to the turbine master control 33 by way of its output 38.
  • the turbine inlet valves are opened' or closed to a greater or lesser extent than commanded by the feedforward signal in order to maintain the throttle pressure at the desired set point.
  • the feedback controller 24 is connected to the summing device 13 through closed contact 18, and the feedback controllers 23 and 25 are disconnected from the respective summing device 12 and 13 because of the open condition of the contacts 17 and 19.
  • the feedforward signal on the output 11 controls the turbine valves without correction; and the firing rate of the boiler is increased or decreased to compensate for variations in the set point pressure, by the feedback signal on the output 21 which is summed with the feedforward signal by the summing device 13 to conduct a corrected or trimmed signal to the manual/automatic controller 35 for governing the boiler firing rate through the boiler master control mechanism 36.
  • the feedback controllers 23 and 25 are connected to the summing devices 12 and 13 respectively through the closed contact 17 and 19; and the feedback controller 24 is disconnected from the summing device 13 because contact 18 is open.
  • the feedforward signal on output 11 of the load demand computer is modified or trimmed by the throttle pressure error signal from the feedback controller 23 to adjust the turbine inlet valves; and also, the feedforward signal 11 to the summing device 13 is modified or trimmed by a megawatt error signal from the feedback controller 25 to adjust the firing rate of the boiler in accordance with any deviation in the desired megawatt output of the plant, as determined by the megawatt detector MW.
  • a transfer from one operating mode to another is initiated by the operation of the appropriate pushbutton BPB, TPB and CPB to govern the transfer circuitry 28 to hold the input signals to the turbine and boiler master controls 33 and 36 to the pre-transfer value to connect and disconnect the feedback controllers 23, 24 and 25, as previously discussed; and to change the output of the load demand computer 10 in accordance with analog input signals on lines 48 or 50 as the case may be; all as described, in detail in connection with FIG. 2, in order that a transfer is effected without disturbing'the position of the turbine inlet valves, boiler firing or megawatt output of the plant.
  • the plant mode transfer circuitry 28 is illustrated as being enclosed by the dashed lines.
  • the portions of the circuitry of FIG. 2 which are common with the circuitry of FIG. I bear similar reference numerals. It is to be understood that, although certain of the components and circuitry are shown in the preferred embodiment as being part of the mode transfer circuitry 28, in actual practice, some or all components may be structured within the feedback controllers 23, 24 and 25, the load demand computer 10, the turbine master control 33, or boiler master control 36, for example.
  • the plant mode transfer circuitry 28 in the described embodiment includes similarly constructed tracking signal selectors 51, 52, 53 and 54, one form of which is shown in FIG. 4.
  • each of the tracking signal selectors may be any well-known analog device which responds to a signal to conduct a selected analog signal at its output.
  • the signal selector 51 functions to conduct an analog signal on its input 50 over its output 30 in response to a digital signal on its input 55.
  • the presence of a signal on its input 36 operates the selector 51 to conduct the analog signal on its input 48 over its output 30; and the presence of a digital signal on its input 56C selects an analog signal on line 57 for input to the LDC 10 over output line 30.
  • the signal on the output 11 of the load demand computer 10 is either increased or decreased in accordance with the value of the signal on line 30.
  • the signal on the output 11 may be either increased or decreased manually by manipulation of the mechanism 26, or either increased or decreased by remote control apparatus of the plant referred to at block 58.
  • the tracking signal selector 52 functions to conduct an analog signal of zero value on its output 41 to the feedback controller 23, as represented by its input 62 in response to a digital signal on its input 60.
  • the presence of a digital signal on input 61 causes the selector 52 to conduct on line 41 the analog signal on its input 63.
  • the input 44 which may be termed a track enable input
  • the controller tracks, or in other words generates at its output 21 an analog signal corresponding to the value of the signal on line 41.
  • the output signal on line 21 corresponds to the difference between the actual throttle pressure and the set point throttle pressure as determined by the signal from the elements TP and SP.
  • a signal of zero potential is input to the controller 24 to generate a zero signal on its output 21 at times when track enable input 45 to the controller 24 is energized.
  • the selector conducts an analog signal on its output 42, which in turn governs the controller 24 to track the value of the signal on input 66 of the selector 53 at times when the track enable input 45 is energized.
  • the controller At times when the input 45 of the controller 24 is deenergized, the controller generates at its output 21 a signal corresponding to the difference between the set point signal represented by element SP and the actual throttle pressure detected by TP.
  • the signal selector 54 functions to conduct a zero signal from its input 74 on its output 43 in response to a digital signal on its input 7 5; and, in response to a digital signal on its input 76, the signal selector 54 conducts a signal representative of the value on its input 77, over its output 43.
  • the controller 25 At times when the track enable input 46 is energized the controller 25 generates an analog signal on its output 22 corresponding to the signal on line 43 which signal corresponds to either zero or the value of the signal on its input 77.
  • the controller 25 At times when the track enable input 46 is deenergized, the controller 25 generates a signal corresponding to the difference between the value of the signal from the load demand computer 10 on its input 78 and the actual megawatt output of the plant as detected by the detector MW.
  • a component 76 which is shown in detail in FIG. 7, may be a standard analog component which conducts a signal at its output 63 which is equal to the valueof an input signal on its line 68 less the value of an input signal on its line 70.
  • the designation (plus) and (minus) adjacent the input 68 and 70 denote that the value of the signal on input 70 is algebraically subtracted from the value of the input signal on line 68.
  • a difference component 71 is similar to the difference component 67 and conducts a signal on its output 66 that corresponds to the value of a signal on its input 72 less the value of a signal on its input 73.
  • the mode transfer circuitry 28 also includes mode select logic circuitry referred to as 80, which is shown in mode detail in FIG. 9; however, the mode select function may be any conventional logic circuitry which functions as herein described.
  • the logic 80 functions to energize its outputs 14, 15 and 16, selectively, to connect and disconnect the feedback controllers 23, 24 and 25 to the summing devices 12 and 13 in accordance with the desired mode of operation in response to the operation of the mode select pushbutton CPB, TPB or BPB.
  • the mode select logic 80 functions to energize its output 64 when the plant is in the turbine-follow mode, its output 81 when the plant is in the boiler-follow mode, and its output 46 when the plant is in the coordinated mode.
  • the remaining components of the plant transfer circuitry 28 together with a detailed description of the method and system of the present invention will be explained in detail in connection with its operation prior to, during and subsequent to a transfer between turbine-follow, boiler-follow and coordinated control modes.
  • the mode select logic 80 is in a condition where the contact 17 in the output 20 of the feedback controller 23 is closed; and the contacts 18 and 19 in the outputs 21 and 22, respectively, of the controllers 24mm 25 are open.
  • the feedforward signal on the output 11 of the load demand computer is input through the summing device 13 and the manual/automatic transfer station 35 to the boiler master control 38 without correction.
  • thefeedforward signal on the output 11 to the summing device 12 is trimmed by a feedback error'signal on the output 20 of the feedback controller 23 to either raise or lower the steam inlet valve'position in accordance with the difference between the actual throttle pressure and the throttle pressure set point. Therefore.
  • the firing rate of the boiler is determined solely in accordance with the value of the feedforward signal on the output 11; and any deviation in the throttle pressure set point is corrected by the raising or lowering of the steam inlet valves.
  • the output 64 of the mode select logic 80 is energized whichresults in the track enable input 45 being energizedand'a zero signal being selected by the signal selector 53 so that the output on line 42 is at zero potential, and the'controller 24 is driven to have zero potential at its output.
  • the input 45 to the controller 24 is energized by a circuit which includes line 64, OR gate 85, line 45 and the controller 24.
  • the controller 25 is driven to zero potential by a circuit which includes the deenergized output 46 from the logic 80, negative function 86, OR gate '87 arid the track enable input 46; and by another circuit which includes OR gate 90, negative function 92 and input line 75 to the signal selector 54.
  • a typical situation may exist with the" plant operating in the turbine-follow mode wherein the valueof the signal on the output 11 of the load demand computer 10-is at 50 percent load for example, and the error signal on line 20 from the feedback controller 23 may be at +10 percent for example. This condition results in a signal of 60 percent at the output 31 of the summing device 12 for input'to the manual/automatic transfer station 32 and to the turbine master control 33 over line 39.
  • the feedforward signal of 50 percent is also conducted to the summing device 13, which is uncorrected by the feedback controller 24 over line 34 to the manual/automatic station 35.
  • the boiler master control is receiving a signal which corresponds to a 50 percent load while the turbine controlis receiving a signal which corresponds to a 60 percent load in order to keep the system properly balanced.
  • the plant can be transferred between operating modes either manually or automatically in response-to a predetermined contingency.
  • the plant system of course, in actual practice, is much more sophisticated in its structure on function; and for the sake of clarity in describing the inventions, only the function necessary to describe the present embodiment of the invenillustrated. .1 I,
  • the line 27 to'the load demand computer 10 is energized which enables the load demand computer to accept and track the output signal'present on the input 30.
  • the manual transfer stations 32 and 35 in response to the energizing of the input 37 prevent any change in the value of the signal on lines 38 and 40 to the input of the turbine master control 33 and the boiler master control 36.
  • the occurrence on the pulse on line 37 also energizes inputs95 96 and 97 to AND gates 98, 99 and 100 respectively.
  • the AND gate 98 conducts in responseto the occurrence of such pulse from the generator 93 because the other input 101 to the AND gate 98 is energized by the operation of the pushbutton BPB as shown in FIG. 1.
  • the conductingof the AND gate 98 applies a digital signal on line 56 to the input of the signal selector 51, which selects the analog signal from the input 50- to be tracked by the load demand computer 10.
  • the operation of the pushbutton BPB energizes an input 102 to the mode select logic 80 which deenergizes its output line 14 to open the contact 17 of the controller 23 to disconnect the feedback circuit from the summing device 12; and energizes its output line 15 to close the contact 18 in the output of the controller 24 to connect the feedback loop to the boiler master control 36 through the summer 13 andthe manual- /automatic station 35. While the input 102 of the mode select logic 80 is energized, all of the outputs 64, 81 and 46 of the mode select logic 80 are deenergized to represent that the plant is not in any one of its operating modes, but being transferred between'modes.
  • the deenergizing of the output line 64 from the mode select logic 80 removes the select zero signal command'from the signal selector 5,3; and the deenergizing of the line 81 removes the select zero command over input 60 to the signal selector 52.
  • the controller 25 remains in the same condition with respect to its input 46 and 43 as it was in the turbine follow mode.
  • the operation of the pushbutton BPB and the occurrence of the pulse at the output of the pulse generator 93 has governed the automatic/manual transfer station 32 and 35 to hold the signals on output 38 and 40 to their pre-transfer value; has operated the load demand computer 10 to track the pretransfer signal on line 38 governing the turbine master control 33; and has disconnected and connected the feedback controllers 23 and 24 respectively.
  • the controller 24 is tracking the signal on input line 66 of the selector 53 from the difference function device '71.
  • the device 71 is conducting a signal equal in value to the pre-transfer value of the signal to the boiler master control 36'less the value of the modified feedforward signal which was tracked prior to transfer.
  • the value of the signal at the output 34 of the summing device 13 is equal to 50 percent which is the same value present previous to the beginning of the transfer; and the output signal on line 31 of device 12, to the turbine master control equal to a 60 percent load signal, which is the pre-transfer value of such signal.
  • the transfer is deemed complete; and the system is placed in the following condition.
  • a negative function 106 to the input of the mode select logic 80 causes the output line 81 of the mode select logic 80 to be energized which is representative of the plant being in the boiler-follow mode.
  • the signal on the output line 81 causes the signal selector 52 to conduct a zero signal on its output 41 to drive the signal on the output 20 of the controller 23 to zero in preparation for the next transfer.
  • AND gate 83 ceases to conduct which deenergizes the track enable input 45 of the controller 44 so that the boiler feedback controller 44 now responds to an error signal corresponding to the actual throttle pressure and the set point throttle pressure for the boiler-follow mode.
  • the pulse generator 93 is activated in response to the operation of the pushbutton CPB, to generate the five second pulse to hold the input signal to the control mechanisms 33 and 38 at their pre-transfer value in the same manner as described in connection with the transfer from the turbine-follow to the boilerfollow mode.
  • the mode select logic 80 is energized through input 107, which energizes the output line 14, deenergizes the output line 15, and energizes the output line 16 so that contacts 17 and 19 are closed and contact 18 is opened in the outputs 20, 21 and 22 respectively of the feedback controllers 23, 24 and 25 to connect both the megawatt and turbine throttle pressure feedback loops to the summing devices 13 and 12 respectively.
  • the track enable input 27 to the LDC computer 10, the track enable input 44 to the feedback controller 23, and the track enable input 45 to the feedback controller 25 is energized.
  • the circuit for energizing the track enable input 27 includes line 37 at the output of the pulse generator 93.
  • the circuit for energizing the track enable input 44 includes the output of the AND gate 100 and the OR gate 110.
  • the circuit for energizing the track enable input 46 includes the output of the AND gate 100, line 108, and OR gate 87.
  • the load demand computer during this transfer tracks the analog signal on input line 57, which signal is connected to the megawatt detector MW and is equal in value to the actual megawatt output of the turbine.
  • the presence of a signal on line 56C at the output of the AND gate 100 selects the signal on the input 57.
  • the controller 23 tracks the analog signal occurring on input 63 to the selector 52 from the difference device 57 during transfer to the coordinated mode.
  • the circuit for selecting the input 63 includes the output of the AND gate 100 and the input 61 to the selector 52.
  • the controller 25 tracks the analog signal on the input 77 to the signal selector 54.
  • the circuit for selecting the signal on the input 77 includes the output of the AND gate 12 100, line 108, the OR gate 90, and the input 76 to the signal selector 54.
  • the value of the signal at the input to the boiler master control previous to the transfer is equivalent to a 60 percent load demand; and assuming that the value of the feedforward signal to the turbine master control 33 previous to the transfer is equivalent to a 50 percent load demand, then the same signal value on each of the inputs to the turbine and boiler master control must be 50 and 60 percent after the transfer.
  • the actual megawatt signal value as detected by the detector MW is equivalent to a percent load. Therefore, during the transfer, the value of the signal on the output 11 of the lload demand computer 10 becomes equal to the actual megawatt signal value which is 70 percent.
  • the difference device 67 operates to subtract the 70 percent megawatt signal from the 50 percent uncorrected pre-transfer feedforward signal resulting in a -20 percent signal on the input 63, which is tracked by the feedback controller 23.
  • the summing device 12 algebraically adds the 70 percent megawatt signal on the output 11 and the 20 percent signal on the output 20 of the controller 23 resulting in a 50 percent load signal on the input 31 to the manual/automatic transfer station 31, which is identical to the value of the pre-transfer signal.
  • the pre-transfer value of the signal to the boiler master control 36 is 60 percent, and the actual megawatt output signal on line 1 1 is 70 percent.
  • the difference device 71 subtracts the 70 percent signal which is input on line 73 from the 60 percent signal which is input on line 72 to the difference device 71.
  • the value of the signal that is tracked by the controller 25 is equal to 1O percent.
  • the summing device 13 during this transfer has a 70 percent signal input from the line 11 and a l0 percent signal from the output 22 of the controller 25, which results in a signal having a 60 percent value on the. input 34 to the manual/automatic transfer station 35. Therefore, the pre-transfer value of the input signal to the boiler master control 36 is identical to the value of the signal on the line 34 which is summed by the sum- 'ming device 13 during the transfer.
  • the output'pulse from the generator 93 ceases which releases the hold on the manual/automatic station 32 and 35.
  • the gate ceases to conduct which removes the signal from the track enable input to the load demandc'om'puter 10, the feedback controller 23, and the feedback controller 25.
  • the load demand computer 10 may be operated through its remote control device 58 or its manual control device 26 for varying the value of the feedforward signal on the output 11; the feedback controller 23 is now generating an error signal corresponding to the value between the throttle pressure set point and the actual throttle pressure", and the feedback controller 25 is generating an error signal corresponding to the difference between the feedforward signalon the output 1 1 and the actual megawatt output of the plant.
  • the pushbutton BPB is operated to generate the 5 second pulse, as described in connection with the other transfers.
  • the feedback controller 25 and the feedback controller 23 are disconnected from the summing devices 12 and 13 while the feedback controller is connected to the summing device 13 by the energizing and deenergizing of the appropriate out- 13 puts 14, 15 and 16 of the logic 80 as previously described. Assuming that prior to the transfer the signal that is input to the turbine master control 33 is 50 percent, and the signal input to the boiler master control 36 is 60 percent, such signals are held at their pretransfer value in response to the presence of the sec ond pulse in the same manner as previously described.
  • the input 56 to the signal selector 61 is energized by the previously described circuit which governs the load demand computer to track the signal on its input 50 which corresponds to the pre-transfer value of the demand signal to the turbine master control 33 which is in the present example 50 percent. Therefore, the signal on the output 11 is changed to be equal to a 50% signal for controlling the turbine master control 33 at the termination of the transfer in the same manner as described in connection with the previous examples.
  • the boiler feedback controller 24 is governed to track an output equivalent to 10 percent which is the tracked signal of 50 percent on the output 11 subtracted from the pre-transfer signal of 60 percent on the input 72 of the difference amplifier 71.
  • the 50 percent signal and the 10 percent signal are added by the summing device 13 to provide a signal equivalent to a 60 percent demand which is the same value of the demand signal present previous to the transfer.
  • the disconnected controllers 23 and are driven to their zero condition at the termination of the transfer by the previously described circuits.
  • FIG. 3 schematically shows the primary functions of the load demand computer insofar as they affect the method and system of the present invention.
  • the energizing of the track enable input 27 conditions AND gates 115 and 1 16 to operate a conventional up/down counter 117, which in turn operates a digitalto-analog converter 118 to generate the analog signal on the output 11.
  • the selected track signal is input to comparators 120 and 121 which is compared to the signal on the output 11 for either operating the up/down counter 117 to either increase or decrease the value of the signal.
  • the manual control device 26 operates the up/down counter 117 directly through OR gates 122 and 123.
  • FIG. 4 illustrates schematically the track signal selector 51 which selects either the actual megawatts, the pre-transfer value of the boiler demand signal or the pre-transfer value of the turbine demand signal to be conducted over its output in response to the energizing of either its input for entering the coordinated, turbine-follow or boiler-follow mode of operation.
  • the energizing of the input 56C closes contacts 130 and 131 of a relay 132 to conduct the signal on input 57 to the output line 30.
  • the signal selectors 52, 53 and 54 may have the same type of an arrangement as the signal selector 51.
  • FIG. 5 illustrates schematically a feedback controller, such as the controller 23.
  • a relay 140 When the track enable input 44 is energized, a relay 140 is closed which conducts the analog signal from the line 41 through the controller circuitry to the output line 20.
  • a relay 141 When the input line 44 is deenergized, a relay 141 is energized which conducts the error signal between the actual throttle pressure and the set point throttle pressure to the output 20. Regardless of the period for integrating the time constant, the controller output is immediate when the track enable input is energized.
  • the other controllers differ with respect to the integration of their time constant, they are all assumed to be similarly constructed.
  • the turbine throttle pressure controller 23 in one practical embodiment integrates its time constant in 15 to 20 seconds, for example.
  • the megawatt controller 25 integrates its time constant in 5 minutes, for example; and the boiler throttle pressure controller 24 integrates its time constant in approximately 3 minutes, for example.
  • FIG. 6 is a schematic arrangement of a conventional summing device, such as the summing device 12 wherein the analog signals on line 11 and 20 are summed to provide the output on lines 31.
  • FIG. 7 is a typical difference device, such as 67, for example, wherein the analog input on line is subtracted from the analog signal on line 68 to generate the difference on the output 63 in a conventional manner.
  • FIG. 8 is a manual/automatic transfer station, such as 32, where an input signal on the line 37 holds the output signal on line 38, for example, by inhibiting the operation of an up/down counter 150.
  • a signal on the input 31 operates the up/- down counter 150, which operates a digital-to-analog converter 151 to provide the proper analog signal on the output 38.
  • the manual/automatic station includes various logic in clocks to perform other functions including switching over from automatic to manual control of the turbine or the boiler, as the case may be, by the operation of the panel buttons referred to at 152.
  • FIG. 9 illustrates schematically one form of the mode select logic circuitry, which includes the various logic gates to energize the various outputs in response to the operation of the pushbuttons BPB, TBP and CBP in the manner described in connection with the operation of the system.
  • Flip-flop circuits 160, 161 and 162 permit the operator to momentarily depress the pushbutton to initiate transfer.
  • the initiation of a transfer generates a pulse of 5 second duration from the output of the generator 93.
  • the presence of the pulse prevents an increase or a decrease in the outputs of the transfer stations 32 and 35 to the input of the boiler and turbine control apparatus 36 and 33.
  • the feedback controllers 23, 24, and 25 are connected and disconnected by the mode select logic depending on the mode that the system is entering.
  • the track enable input to the computer 10 is energized; and the track enable input to the feedback controllers which are to be placed in service upon termination of the transfer are energized.
  • the feedforward signal from the load demand computer 10 is increased or decreased to equal the analog signal selected by the signal selector 51. This signal is equal to the pre-transfer or held output of the manual/automatic station which will receive an uncorrected feedforward signal at termination of the transfer.
  • the signal is equal to the actual megawatt output of the plant.
  • the feedback controllers 23, 24 or 25, depending on the mode the system is entering tracks a selected signal input to its associated signal selector 52, 53, and 54. This tracked signal is equal to the held output on its associated transfer station 32 and 35 less the tracked signal generated by the computer 10. The tracked output signal from the feedback controller is summed with the tracked signal from the computer 10 by its associated summing device 12 and 13.
  • the pulse from generator 93 terminates which permits the manual- [automatic stations 32 and 35 to respond to variations in their inputs 31 and 34, and the tracking function of the inservice feedback controller is removed.
  • first circuit means including each feedback loop to modify the value of the input signal to the boiler and turbine apparatus in accordance with the output signal value of its associated feedback loop that is in service for a distinct operating mode
  • mode transfer selection means effective when activated to govern the turbine and boiler control apparatus to be unresponsive to a change in the value of either a feedforward or feedback signal to prevent any change in turbine valve position and boiler firing rate during a mode transfer
  • second circuit means including the feedforward signal generating means governed by the activation of the transfer means to modify the generated feedforward signal to be representative of a selected value in accordance with the operating mode selected by the mode transfer means,
  • third circuit means governed by the activated transfer means to control each feedback loop put in service in accordance with the selected operating mode to generate a feedback output signal for the first circuit means having a value to modify the input signal for the turbine and boiler control apparatus to be representative of the value of the turbine and boiler control apparatus input signal upon activation of the transfer means, and
  • a system according to claim 1 wherein the first circuit means includes a summing device for algebraically adding the feedforward signal and the output of the in service feedback loop.
  • a system according to claim 1 further comprising an analog signal generating device for each control apparatus responsive to the signal from the first and second circuit means to govern the value of the input signal for its associated control apparatus, and each said device includes means responsive to the activation of the transfer selection means to hold the output of the analog signal generating device stationary while the transfer selection means is activated.
  • a system according to claim 1 wherein the transfer selection means and the transfer deactivating means includes a pulse generator for generating a selected pulse of a predetermined time duration, and the transfer selection means is activated during the time duration of the generated pulse only.
  • each feedback loop includes a proportional plus integral controller
  • the third circuit means includes a difference function device for each control apparatus governed by input signals representing the value of the input signal of its associated control apparatus upon activation of l the transfer selection means and the value of the feedforward signal modified by the second circuit means to conduct a difference signal, and the controller is governed by the value of the difference signal while the transfer selection means is activated to generate the value of such difference signal at its output.
  • a system for transferring from one operating mode to another rapidly and without disturbing the plant process of a boiler-turbine power plant comprising a load demand signal generator operative to generate an output signal having a value corresponding to a desired plant load, said device having means to increase and decrease the output signal in accordance with the value of a selected tracking signal,
  • a turbine control apparatus and a boiler control apparatus each operative to govern the operation of the boiler and the turbine respectively in accordance with the value of an input signal
  • a throttle pressure feedback controller for each control apparatus operative to generate an error signal representative of the required change in the desired load signal for its associated apparatus to operate its respective turbine and boiler to maintain a predetermined throttle pressure, each said controller also having means to generate an error signal in accordance with the value of a selected tracking signal,
  • each control apparatus connected at one input to receive the error signal from 17 its associated feedback Controller and connected at anotherinput to receive the desired load signal from the generator, each said device being operative to generate an output signal corresponding to the algebraic sum of the value of the input signals,
  • each control apparatus connected at its input to theoutput signal of its associated summing device, said signal generator being operatively connected to generate a demand signal for its associated apparatus in accordance with the value of the signal from the summing device, each said device also including a holding means when activated to prevent the output signal to its associated control apparatus from responding to a change in its input signal,
  • each control apparatus having one input connected electrically between the output of its associated summing device and another input connected to the output of the load demand generator, each said device being operative to generate at its output a signal representative of the value of the signal at its one input less the value of the signal on its other input,
  • transfer means operative when activated to initiate a transfer to a selected operating mode
  • a system according to claim 9 further comprising a megawatt feedback controller for the boiler control apparatus operative to generate an error signal representative of the required change in the load signal for the boiler control apparatus to operate the boiler control apparatus to govern the turbine to maintain a predetermined power output, said feedback controller also having means to generate an error signal in accordance with the value of a selected tracking signal,
  • a method of transferring rapidly from one to another of at least two modes of operation in a boiler-turbine power plant without disturbing the plant process wherein a control signal representative of desired plant load is generated to control in parallel the boiler portion of the plant and the steam turbine portion of the plant in both of the modes and a feedback loop modifies the control signal to the boiler only in one of the modes and a feedback loop modifies the control signal to the turbine only in the other mode, said method comprising holding the load demand signals to both the boiler and turbine at their pre-transfer value to prevent a change in their value during the transfer,
  • a method according to claim 12 wherein the changed feedforward signal is representative of the actual power output of the plant at times when the transfer effects the trimming of the load demand signal to both the turbine and boiler.
  • a method according to claim 12 wherein the changed feedforward signal is representative of the pretransfer trimmed load demand signal at times when the transfer effects the trimming of the other of the boiler turbine load demand signals only.
  • a system for transferring from one operating mode to another rapidly and without disturbing the plant process of a boiler turbine power plant wherein selected connected feedback loops trim a feedforward signal to provide a load demand signal for controlling I the boiler and turbine in each operating mode; said sys tem comprising means to initiate a transfer from one mode to another, means responsive to the initiation of a transfer to hold the load demand signals to the boiler and turbine at a constant value during the transfer,

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Control Of Turbines (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
  • Feedback Control In General (AREA)
US556363A 1975-03-07 1975-03-07 System and method for transferring between boiler-turbine plant control modes Expired - Lifetime US3925645A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US556363A US3925645A (en) 1975-03-07 1975-03-07 System and method for transferring between boiler-turbine plant control modes
FR7606141A FR2303157A1 (fr) 1975-03-07 1976-03-04 Systeme et methode de passage d'un mode de conduite a un autre dans des installations de turbine a chaudieres
BE1007229A BE839221A (fr) 1975-03-07 1976-03-05 Systeme et methode de passage d'un mode de conduite a un autre dans des installations de turbines a chaudieres
IT20904/76A IT1056907B (it) 1975-03-07 1976-03-05 Sistema e metodoi di trasferimento tra i nodi di regolazione di una centrale termoelettrica su caldaia e su turbina
JP51023351A JPS5917242B2 (ja) 1975-03-07 1976-03-05 ボイラ・タ−ビン設備の制御モ−ド変換システム

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US4179742A (en) * 1978-04-06 1979-12-18 Westinghouse Electric Corp. System for intelligently selecting the mode of control of a power plant
US4470257A (en) * 1982-04-30 1984-09-11 Westinghouse Electric Corp. Isochronous and droop speed control for a combustion turbine
US4550380A (en) * 1983-12-16 1985-10-29 Westinghouse Electric Corp. Microprocessor-based extraction turbine control
US4607325A (en) * 1981-10-21 1986-08-19 Honeywell Inc. Discontinuous optimization procedure modelling the run-idle status of plural process components
US20090037029A1 (en) * 2006-01-11 2009-02-05 Garay Mauricio Method for operating a firing plant
CN101825005A (zh) * 2010-04-26 2010-09-08 浙江国华浙能发电有限公司 一种火力发电机组中高压旁路的运行控制方法
CN102235657A (zh) * 2010-04-26 2011-11-09 中国神华能源股份有限公司 一种提高电站锅炉可靠性的控制方法
US20120046762A1 (en) * 2010-08-18 2012-02-23 International Business Machines Corporation Performance improvement of signal transformation schemes for ultra-fast scanning
CN108224398A (zh) * 2016-12-15 2018-06-29 中电华创电力技术研究有限公司 一种火电机组动态前馈协调控制方法
CN112503567A (zh) * 2020-11-24 2021-03-16 北方魏家峁煤电有限责任公司 锅炉主控指令的前馈系数确定方法及装置

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JPS5540229A (en) * 1978-09-14 1980-03-21 Hitachi Ltd Output control system of pressure-variation operating boiler turbine power plant

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US3564273A (en) * 1967-11-09 1971-02-16 Gen Electric Pulse width modulated control system with external feedback and mechanical memory
US3555251A (en) * 1967-12-06 1971-01-12 Honeywell Inc Optimizing system for a plurality of temperature conditioning apparatuses
US3588265A (en) * 1968-04-19 1971-06-28 Westinghouse Electric Corp System and method for providing steam turbine operation with improved dynamics
US3561216A (en) * 1969-03-19 1971-02-09 Gen Electric Thermal stress controlled loading of steam turbine-generators
US3552872A (en) * 1969-04-14 1971-01-05 Westinghouse Electric Corp Computer positioning control system with manual backup control especially adapted for operating steam turbine valves

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4179742A (en) * 1978-04-06 1979-12-18 Westinghouse Electric Corp. System for intelligently selecting the mode of control of a power plant
US4607325A (en) * 1981-10-21 1986-08-19 Honeywell Inc. Discontinuous optimization procedure modelling the run-idle status of plural process components
US4470257A (en) * 1982-04-30 1984-09-11 Westinghouse Electric Corp. Isochronous and droop speed control for a combustion turbine
US4550380A (en) * 1983-12-16 1985-10-29 Westinghouse Electric Corp. Microprocessor-based extraction turbine control
US8783042B2 (en) * 2006-01-11 2014-07-22 Alstom Technology Ltd Method for operating a firing plant
US20130019605A1 (en) * 2006-01-11 2013-01-24 Garay Mauricio Method for operating a firing plant
US20090037029A1 (en) * 2006-01-11 2009-02-05 Garay Mauricio Method for operating a firing plant
CN101825005A (zh) * 2010-04-26 2010-09-08 浙江国华浙能发电有限公司 一种火力发电机组中高压旁路的运行控制方法
CN102235657A (zh) * 2010-04-26 2011-11-09 中国神华能源股份有限公司 一种提高电站锅炉可靠性的控制方法
CN101825005B (zh) * 2010-04-26 2012-07-18 中国神华能源股份有限公司 一种火力发电机组中高压旁路的运行控制方法
CN102235657B (zh) * 2010-04-26 2013-08-28 中国神华能源股份有限公司 一种提高电站锅炉可靠性的控制方法
US20120046762A1 (en) * 2010-08-18 2012-02-23 International Business Machines Corporation Performance improvement of signal transformation schemes for ultra-fast scanning
US8401676B2 (en) * 2010-08-18 2013-03-19 International Business Machines Corporation Performance improvement of signal transformation schemes for ultra-fast scanning
CN108224398A (zh) * 2016-12-15 2018-06-29 中电华创电力技术研究有限公司 一种火电机组动态前馈协调控制方法
CN112503567A (zh) * 2020-11-24 2021-03-16 北方魏家峁煤电有限责任公司 锅炉主控指令的前馈系数确定方法及装置
CN112503567B (zh) * 2020-11-24 2022-10-28 北方魏家峁煤电有限责任公司 锅炉主控指令的前馈系数确定方法及装置

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IT1056907B (it) 1982-02-20
FR2303157A1 (fr) 1976-10-01
JPS51113049A (en) 1976-10-05
JPS5917242B2 (ja) 1984-04-20
BE839221A (fr) 1976-09-06

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