Hitachi, Ltd.

Shoei Takahashi

Isao Sato

Fumiyuki Hirose

Hiraku Ikeda

Katsuhito Shimizu

Yoshio Maruyama

Akira Shimura

Tohru Akatsu

Minoru Takaba

Kazuyasu Asakura

Yukiko Mori

Kazuhiko Miura

Michio Kuroda

Nobuyuki Iizuka

Kazuhiko Kumata

Yoshiharu Nakayama

Hideyuki Kawamura

Takeshi Ishida

Toshihiko Harashima

A multiplexing control system has a common process input/output unit for distributing process signals from sensors for measuring the same state variable of a process to digital controllers. One process input/output unit for inputting/outputting a process signal between the multiplexing control system and plant is provided for each process signal. The process input/output unit for the process signal of high importance is triplexed. A process controller having an operating function is provided to each of the triplexed process input/output units. A process input/output unit for the process signal of intermediate importance is diplexed. A process input/output unit for the process signal of low importance is monoplexed. The process signals of the diplexed process input/output units and the monoplexed process input/output unit are controlled by a controller having a master right among the process controllers.

Multiplexing control system and multiplexing method therefor

The invention suppresses the production of thermal stress in power generating equipment and the unstable behavior of the power generating equipment due to the variation of system frequency and stabilizes the system frequency. A power plant load control system controls the operation of a power plant equipped with a gas turbine comprising a combustor (,) and a turbine (,), and a power generator (,) disposed coaxially with the turbine. The power plant load control system comprises a governor load control unit (,) for determining a governor instruction (,) on the basis of the deviation of generated power (,) from a power generation instruction (,) given thereto by a central load dispatching station according to the variation of system frequency, and for determining a fuel supply rate instruction (,) corresponding to a speed droop ratio (R) according to the deviation of shaft speed (,) from a governor instruction (,). The governor load control unit (,) has a fuel supply rate instruction limiter (,) for limiting the change rate of the fuel supply rate instruction (,). The fuel supply rate instruction limiter (,) determines a limit to the change rate so that the production of thermal stress in the gas turbine and unstable combustion may be suppressed, and limits the variation of the fuel supply rate instruction (,) to a range below the limit.

Method of controlling load on power plant and load control system for carrying out the same

A gas turbine engine control method and apparatus as disclosed for optimizing fuel/air mixture, especially during decreasing load conditions. In a large capacity gas turbine engine system used for generation of electric power, the system is designed to operate at a relatively constant rotational speed of the turbine which drives an electric generator unit. The load of the turbine engine varies throughout the day due to changes in electrical power demands. During normal rated load conditions, the control of the fuel/air mixture is by way of changes in fuel supply, corrected to return the turbine exhaust temperature to a desired rated temperature. During this mode of operation, the compressor inlet guide vanes are maintained in a substantially constant open position. For accommodating decreasing load conditions where the temperature drops below a predetermined temperature level below the rated temperature operation, the system is switched to an inlet guide vane control mode of operation. During the guide vane control mode of operation, the inlet guide vanes are controlled at a more precise temperature correction sensitivity than is the case for normal load operations. This more precise inlet guide vane control during decreasing load conditions assures improved fuel/air mixture during decreasing load and consequent improved efficiency and minimal NO.sub.x compound emissions, especially during changing ambient temperature conditions where cold air would otherwise increase the air supply.

Gas turbine control method and apparatus

A method for controlling a gas turbine combustor which comprises nozzles for injecting fuel into a combustor and which serves to combust the fuel with air in a combustion chamber so as to rotatively drive a gas turbine by combustion gas compressed as a result of combustion of a fuel, wherein the ratio of a flow rate of fuel supplied into the combustor to a flow rate of air supplied into the combustor is changed in accordance with at least one of the states of fuel, air and rotational frequency of the turbine.

Method for controlling gas turbine combustor

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Hitachi, Japan

Shoei Takahashi