System and method for operating a steam turbine with digital computer control having integrator limit

An electric power generating system comprising:

• a. a steam turbine system;
• b. a steam generator for providing steam to said steam turbine system;
• c. an electric generator rotated by said turbine system and adapted to be connected to an electric load;
• d. means for digitally computing and processing, having a central processor unit and a memory interconnected with said central processor unit;
• e. means for converting input signals to digital data, said input converting means being connected to said digital computing means;
• f. means for converting digital data to output signals, said digital to output converting means being connected to said digital computing means;
• g. means for sensing the value of at least one predetermined generating system operating parameter, and for generating input signals representative of said parameter, said sensing means being connected to said input converting means;
• h. means for developing a signal representative of the desired condition of said parameter, said means for developing being connected to said input converting means;
• i. means for controlling the steam flow to said turbine;
• and
• j. means for connecting said output signal converting means to said steam flow control means;
• k. said digital computer means being programmed to perform the functions of
• i. developing a difference signal representative of the differential between desired and present conditions of at least one turbine operating parameter,
• ii. integrating said difference signal,
• iii. limiting said integrated difference signal to a specified range corresponding to extreme conditions of said steam control means, and
• iv. generating control signals in response to said limited integrated signal;
• l. said control signals being converted to output signals by said output converting means for controlling said steam flow control means as a function of said parameter so as to control steam flow as an intermediate variable, and to control turbine and generator speed and load as end operating variables.

Apparatus for monitoring an electric power generating system, said system having a steam turbine system, a steam generator for providing steam to said steam turbine system, and an electric generator rotated by said turbine system and adapted to be connected to an electric load, comprising:

• a. control means for developing signals representative of the difference between desired and actual conditions of at least on specified generating system operating parameter;
• b. digital computer means for translating said difference signals into control signals, said computer means having a proportional plus integral feedback controller including an integrater, means for limiting the output signals of said integrator to a specified range, means for combining said limited integration signals with signals proportional to said difference signals, and feedback means further for comparing the combined signals with said difference signals;
• and
• c. means responsive to said control signals for varying steam flow in said turbine system, whereby turbine and generator speed and load are controlled as end operating variables.

A steam turbine system comprising:

• a. a steam turbine adapted to receive steam from a steam generator;
• and
• b. means for controlling steam flow to said steam turbine, said controlling means including digital computer means programmed to perform the functions of
• i. developing a difference signal representative of the differential between desired and actual conditions of at least one turbine operating parameter,
• ii. numerically integrating said difference signal,
• iii. limiting said integrated signal to a specified range;
• /and/
• iv. /generating control signals in response to said limited integrated signal/multiplying said difference signal by a predetermined factor, and combining said multiplied signal with said integrated signal;
• and
• v. generating a control signal in response to said combined signal.

In an electric power generating system having a steam turbine, a steam generator for providing steam to said turbine, an electric generator rotated by said turbine to drive an electric load, and a digital computer for controlling said generating system, the control method comprising the steps of:

• a. sensing periodically the actual value of at least one specified generating system operating parameter;
• b. providing periodically corresponding desired values for said parameter;
• c. evaluating the difference between associated actual and desired values of said parameter;
• d. integrating numerically in said digital computer the differences from said evaluating step;
• e. limiting said integrated differences to a predetermined range corresponding to select steam flow conditions between said steam generator and said turbine;
• f. generating control signals for said steam flow conditions, to control said parameter toward its desired value;
• and
• g. manipulating said steam flow conditions in response to said control signals.

A method for controlling a steam turbine system comprising the steps of:

• a. developing a signal representative of the difference between desired and actual conditions of at least one specified system operating parameter;
• b. periodically translating in a digital computer said difference signal into a control/signals/signal for said turbine, said translating step including numerically integrating/, in a digital computer/said difference signal/,/ and limiting the integrated/signals/signal to a specified range corresponding to extreme steam flow conditions in said turbine generating a signal proportional to said difference signal and combining said limited integration signal with said proportional signal, and subtracting said combined signal in feedback relation from the next difference signal prior to the next subsequent performance of said translating step;
• and
• c. varying steam flow in said turbine system as a function of said control signal/said steam flow condition to control steam flow as an intermediate variable and turbine speed and load as an end variable/.