Abstract: An object is to maintain a constant gas turbine output without requiring a complicated procedure on site and without being affected by variations in the output of a steam turbine during a reverse-washing/normal-washing switching period of a condenser. A gas turbine control system for a single-shaft combined cycle plant generates a gas turbine output command using a parameter reflecting a gas turbine output during a reverse-washing/normal-washing switching period of a condenser and generates the gas turbine output command on the basis of a generator output command and a steam turbine output during a period other than the reverse-washing/normal-washing switching period of the condenser.

Abstract: An object is to maintain a constant gas turbine output without requiring a complicated procedure on site and without being affected by variations in the output of a steam turbine during a reverse-washing/normal-washing switching period of a condenser. A gas turbine control system for a single-shaft combined cycle plant generates a gas turbine output command using a parameter reflecting a gas turbine output during a reverse-washing/normal-washing switching period of a condenser and generates the gas turbine output command on the basis of a generator output command and a steam turbine output during a period other than the reverse-washing/normal-washing switching period of the condenser.

Abstract: A combustor 10 is furnished with steam cooling piping 11. Steam is flowed by the following route, steam supply piping 20?steam cooling piping 11?steam discharge piping 70, to cool the combustor 10 with steam. When a gas turbine is stopped, valves V73, V71, V51, etc. are closed to construct a closed piping line composed of the pipings 20, 11 and 70. Then, the valve V71 is opened for evacuation by a condenser 90. Then, the valve V71 is closed, and the valve V51 is opened to charge nitrogen into the pipings 20, 11, 70. Then, the valve V51 is closed. By this procedure, residual steam within the steam cooling piping 11 can be reliably removed, and replaced by nitrogen. Thus, during stoppage of the gas turbine, residual steam can be removed reliably and promptly.