Patent ID: 11933197
Assignee: MITSUBISHI ELECTRIC CORPORATION
Field: Engines, pumps, turbines (Mechanical engineering)
Classification: CPC F  Y | IPC F

Claim 12:
13. A combined cycle plant comprising:
a gas turbine configured to be driven by fuel supply;
a waste heat recovery boiler configured to generate steam by using heat from exhaust gas exhausted from the gas turbine;
a steam turbine configured to be driven by the steam from the waste heat recovery boiler;
a condenser configured to return the steam exhausted from the steam turbine to water;
a generator configured to generate electricity by drive of the steam turbine;
a circuit breaker configured to electrically connect the generator to a power system in response to an external command and to electrically disconnect the generator from the power system in response to an external command;
a fuel control valve configured to adjust a flow rate of fuel to be supplied to the gas turbine;
a main steam line configured to guide the steam from the waste heat recovery boiler to the steam turbine;
a steam control valve provided in the main steam line and configured to adjust a flow rate of the steam flowing into the steam turbine;
a thermometer provided in the main steam line closer to the waste heat recovery boiler than the steam control valve and configured to detect a temperature of the steam flowing through the main steam line;
a rotational speed meter configured to detect a rotational speed of the steam turbine;
an output gauge configured to detect an output that is an amount of power generated by the generator; and
a control device, wherein
the control device includes
a start-up fuel control unit configured to command the fuel control valve to start fuel supply to the gas turbine and command the fuel control valve on a flow rate of fuel to be supplied to the gas turbine so that the output of the gas turbine increases to a rated output,
a steam admission command unit configured to command the steam control valve to open so as to start steam supply to the steam turbine when the temperature of the steam detected by the thermometer reaches or exceeds a predetermined temperature,
a synchronization command unit configured to command the circuit breaker to electrically connect the generator to the power system when the rotational speed detected by the rotational speed meter reaches a rated rotational speed of the steam turbine,
an ST generator output control unit configured to command the steam control valve on a flow rate of the steam to flow into the steam turbine after the generator is electrically connected to the power system so that the output detected by the output gauge increases according to a target output change pattern, and
a thermal stress estimating unit configured to estimate thermal stress generated in the steam turbine based on the temperature of the steam detected by the thermometer, and
when the thermal stress estimated by the thermal stress estimating unit reaches or exceeds a predetermined value, the ST generator output control unit commands the steam control valve on the flow rate of the steam to flow into the steam turbine so that a change in the output detected by the output gauge is smaller than a change indicated by the target output change pattern.