Controlling apparatus and starting method

A controlling apparatus to control a combined cycle power-generating plant, the combined cycle power-generating plant comprising:

• a gas turbine;
• an heat recovery steam generator that recovers heat from exhaust gas of the gas turbine and generates steam;
• and a steam turbine that is driven by the steam generated by the heat recovery steam generator,
• wherein the controlling apparatus comprises a controller that controls an output of the gas turbine,
• the controller controls the output of the gas turbine at a second output value that is greater than a first output value, after a paralleling of a power generator of the gas turbine, the first output value being a gas turbine output when an exhaust gas temperature of the gas turbine falls within a temperature range that is determined based on a metal temperature of the steam turbine, and
• the controller controls the output of the gas turbine at the first output value, in a case where a temperature of the steam generated by the heat recovery steam generator exceeds a temperature based on the metal temperature.