COMBINED CYCLE PLANT, ITS CONTROLLING METHOD AND ITS CONTROL DEVICE

摘要

PROBLEM TO BE SOLVED: To prevent a control system from becoming unstable during start-up process of a steam turbine.SOLUTION: A first steam turbine 31 and a second steam turbine 32 of a combined cycle plant are connected to each other by a reheat steam line 42 through a reheat part 26 of an exhaust heat recovery boiler 20, and the reheat steam line 42 and a condenser 36 are connected by a second bypass line 52. A control device 100 comprises: a determination part 111 for determining whether or not a flow rate of the first steam flowing into the first steam turbine 31 becomes a specified flow rate; a command output part 112 for outputting a closing command to indicate that an opened state ventilator valve 71 arranged at the second bypass line 52 should be transferred to a closed state when it is determined that the flow rate of the first steam flowing into the first steam turbine 31 becomes a specified flow rate; and a threshold change part 114 in which a threshold determined by the determination part 111 whether or not the flow rate becomes the specified flow rate is changed while a positive correlation being kept against a temperature of the first steam.