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

Claim 1

A system for transferring a boiler turbine power plant from one operating mode to another rapidly without disturbing the plant process wherein predetermined selected in service feedback loops trim a feedforward signal for controlling the boiler and turbine in each operating mode and at least one feedback loop is put in service for changing operating modes, said system comprising a turbine control apparatus for controlling turbine inlet valve position in accordance with the value of an input signal, a boiler control apparatus for controlling boiler firing rate in accordance with the value of an input signal, means to generate a feedforward signal representative of desired plant operation connected electrically to input the feedforward signal to the boiler and turbine control apparatus in parallel, at least one feedback loop for each control apparatus to generate an output signal, 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 means deactivating the transfer means to render the boiler and turbine control apparatus responsive to their respective input signal from the signal generating means as modified by the first circuit means.

Claim 2

A system for transferring a boiler turbine power plant from one operating mode to another rapidly without disturbing the plant process wherein predetermined selected in service feedback loops trim a feedforward signal for controlling the boiler and turbine in each operating mode and at least one feedback loop is put in service for changing operating modes, said system comprising a turbine control apparatus for controlling turbine inlet valve position in accordance with the value of an input signal, a boiler control apparatus for controlling boiler firing rate in accordance with the value of an input signal, means to generate a feedforward signal representative of desired plant operation connected electrically to input the feedforward signal to the boiler and turbine control apparatus in parallel, at least one feedback loop for each control apparatus to generate an output signal, 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 means deactivating the transfer means to render the boiler and turbine control apparatus responsive to their respective input signal from the signal generating means as modified by the first circuit means.

Claim 10

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, a summing device for each control apparatus connected at one input to receive the error signal from its associated feedback controller and connected at another input 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, an analog signal generator for each control apparatus connected at its input to the output 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, a difference function device for 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, means responsive to the activation of the transfer means to activate the holding means of each analog signal generator, means governed by the activation of the transfer means to connect and disconnect selected feedback controllers to and from their respective summing devices in accordance with the selected mode, means governed by the activation of the transfer means to increase or decrease the desired load signal at the input to each summing device to track the value of the signal at the output of the analog signal generator for the control apparatus disconnected from the output of a feedback controller upon deactivation of the transfer means, means governed by the activation of the transfer means to operate the feedback controller to be connected to its summing device in accordance with a selected mode to track the signal at the output of the difference device, and means deactivating the transfer means, whereby the signal to the input of each analog device upon deactivation of the transfer means is representative of the input signal upon activation of the transfer means.

Claim 11

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, a summing device for each control apparatus connected at one input to receive the error signal from its associated feedback controller and connected at another input 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, an analog signal generator for each control apparatus connected at its input to the output 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, a difference function device for 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, means responsive to the activation of the transfer means to activate the holding means of each analog signal generator, means governed by the activation of the transfer means to connect and disconnect selected feedback controllers to and from their respective summing devices in accordance with the selected mode, means governed by the activation of the transfer means to increase or decrease the desired load signal at the input to each summing device to track the value of the signal at the output of the analog signal generator for the control apparatus disconnected from the output of a feedback controller upon deactivation of the transfer means, means governed by the activation of the transfer means to operate the feedback controller to be connected to its summing device in accordance with a selected mode to track the signal at the output of the difference device, and means deactivating the transfer means, whereby the signal to the input of each analog device upon deactivation of the transfer means is representative of the input signal upon activation of the transfer means.

Claim 13

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, changing the connection of the feedback loops from one of the portions of the plant to the other, changing the desired load signal to be representative of the value of the pre-transfer modified demand signal for one of the portions of the plant generating a feedback signal for the other portion representative of the value of the pre-transfer load demand signal to said portion less the value of the desired load signal, and releasing the hold on the load demand signals to both the boiler and turbine, whereby the load demand signal to both the boiler and turbine is the same before and after the changing of the feedback loops from one to the other of the elements.

Claim 14

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, changing the connection of the feedback loops from one of the portions of the plant to the other, changing the desired load signal to be representative of the value of the pre-transfer modified demand signal for one of the portions of the plant generating a feedback signal for the other portion representative of the value of the pre-transfer load demand signal to said portion less the value of the desired load signal, and releasing the hold on the load demand signals to both the boiler and turbine, whereby the load demand signal to both the boiler and turbine is the same before and after the changing of the feedback loops from one to the other of the elements.

Claim 15

A method of transferring from one operating mode to another rapidly and without disturbing the plant process of a boiler turbine power plant, wherein selected feedback loops trim a feedforward signal to provide a load demand signal for controlling the boiler and turbine in each operating mode, said method comprising holding the load demand signal to the boiler and turbine at a constant value during the transfer, changing the feedforward signal to be representative of a selected value, generating a feedback signal having a value, which when summed the feedforward signal is representative of the value of the load demand signals held during the transfer, summing the generated feedback signals with the changed feedforward signal for the loops to be put in service upon termination of the transfer, and releasing the hold on the load demand signals to terminate the transfer.

Claim 16

A method of transferring from one operating mode to another rapidly and without disturbing the plant process of a boiler turbine power plant, wherein selected feedback loops trim a feedforward signal to provide a load demand signal for controlling the boiler and turbine in each operating mode, said method comprising holding the load demand signal to the boiler and turbine at a constant value during the transfer, changing the feedforward signal to be representative of a selected value, generating a feedback signal having a value, which when summed the feedforward signal is representative of the value of the load demand signals held during the transfer, summing the generated feedback signals with the changed feedforward signal for the loops to be put in service upon termination of the transfer, and releasing the hold on the load demand signals to terminate the transfer.

Claim 19

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 the boiler and turbine in each operating mode; said system 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, means governed by the initiation of a transfer to change the feedforward signal to be representative of a selected value, means to generate another signal for each feedback loop to be connected in accordance with the selected operating mode, said signal having a value which when summed with the changed feedforward signal is representative of the value of the load demand signal held at the constant value, means to sum the feedforward signal and the other feedback generated signal for the selected connected loops, and means to release the hold on the load demand signal at termination of the transfer.

Claim 20

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 the boiler and turbine in each operating mode; said system 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, means governed by the initiation of a transfer to change the feedforward signal to be representative of a selected value, means to generate another signal for each feedback loop to be connected in accordance with the selected operating mode, said signal having a value which when summed with the changed feedforward signal is representative of the value of the load demand signal held at the constant value, means to sum the feedforward signal and the other feedback generated signal for the selected connected loops, and means to release the hold on the load demand signal at termination of the transfer.