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

Abstract

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.