GAS TURBINE CONTROLLER OF SINGLE-SHAFT COMBINED CYCLE POWER GENERATING PLANT AND GAS TURBINE OUTPUT CALCULATING METHOD

A gas turbine control apparatus for a single-shaft type combined cycle power plant is provided by which gas turbine output is accurately computed during a circulating water reversing wash operation. Vacuum down amount is computed from a generator output signal (31) immediately before the mentioned reversing wash operation and is corrected by being multiplied by a valve opening correction factor computed from a condenser reversing valve opening signal (41) and a sea water temperature correction factor computed from a condenser reversing valve inlet sea water temperature signal (47). A condenser vacuum at the time of the reversing wash operation is computed by the corrected vacuum down amount being subtracted therefrom. A vacuum correction factor is computed based on the computed condenser vacuum. A reference steam turbine output is computed based on a post-intercept valve steam pressure signal (34) and a steam turbine output signal (54) is computed by multiplying the reference steam turbine output by the vacuum correction factor. A gas turbine output signal (55) is computed by subtracting the steam turbine output signal (54) from the generator output signal (31).