Combined cycle power plant and start-up method of the same

A combined cycle power plant comprising:

• a gas turbine that is driven with hot gas generated using fuel gas;
• a high-pressure steam turbine and an intermediate-pressure steam turbine that are driven with steam;
• a generator that converts rotative power of the gas turbine, the high-pressure steam turbine, and the intermediate-pressure steam turbine into electric power;
• an exhaust heat recovery boiler that uses exhaust gas from the gas turbine as a heat source, and includes a high-pressure superheater which superheats high-pressure steam and supplies a superheated steam to the high-pressure steam turbine, and a reheater which reheats exhaust steam from the high-pressure steam turbine and supplies a reheated steam to the intermediate-pressure steam turbine;
• a plurality of bypass paths through which the steam or the exhaust gas bypasses each of the high-pressure superheater and the reheater;
• a plurality of bypass flow regulators that regulate flow rates of the steam or the exhaust gas which flows through the plurality of bypass paths;
• a bypass controller that controls the plurality of bypass flow regulators such that a difference between a thermal effect-amount margin of the high-pressure steam turbine and a thermal effect-amount margin of the intermediate-pressure steam turbine is smaller than a predetermined value set in advance;
• a fuel gas regulating valve and a turbine control valve that regulate a plant load;
• a load controller that controls the fuel gas regulating valve and the turbine control valve;
• a measuring instrument that measures a state quantity of the plant;
• a prediction calculator that calculates a predicted value of an amount of thermal effect of the high-pressure steam turbine and a predicted value of an amount of thermal effect of the intermediate-pressure steam turbine, based on the state quantity of the plant measured by the measuring instrument;
• and
• a thermal effect-amount margin calculator that calculates the thermal effect-amount margin of the high-pressure steam turbine and the thermal effect-amount margin of the intermediate-pressure steam turbine, based on the predicted value of the amount of the thermal effect of the high-pressure steam turbine and the predicted value of the amount of the thermal effect of the intermediate-pressure steam turbine calculated by the prediction calculator,
• wherein the bypass controller controls the plurality of bypass flow regulators, based on the thermal effect-amount margin of the high-pressure steam turbine and the thermal effect-amount margin of the intermediate-pressure steam turbine calculated by the thermal effect-amount margin calculator, such that a difference between the margins is smaller than the predetermined value, and
• wherein the load controller controls the fuel gas regulating valve and the turbine control valve, based on the thermal effect-amount margin of the high-pressure steam turbine and the thermal effect-amount margin of the intermediate-pressure steam turbine adjusted by controlling the plurality of bypass flow regulators.