A power plant including: a steam generation device , a turbine which is driven with stream generated by the steam generation device , a condenser which condenses the steam exhausted from the turbine , a feed water heater which heats condensate whose pressure is risen by a condensate pump , a deaerator which heats and de-aerates the condensate heated by the feed water heater , a deaerator water level control valve which controls a water level of the deaerator , an extraction system which introduces the steam extracted from the turbine into the feed water heater , and an extraction valve installed in the extraction system , characterized in that the power plant comprises: an auxiliary steam introduction system which introduces auxiliary steam into the feed water heater ; an auxiliary steam control valve which is installed in the auxiliary steam introduction system and controls an amount of steam supplied to the feed water heater ; and a control device which outputs opening command signals to the deaerator water level control valve , the extraction valve , and the auxiliary steam control valve , wherein the control device controls the extraction valve in a closing direction, controls to maintain an opening of the deaerator water level control valve , and controls the auxiliary steam control valve in an opening direction in a case where a rapid load increase request is made to the power plant. a steam generation device , a turbine which is driven with stream generated by the steam generation device , a condenser which condenses the steam exhausted from the turbine , a feed water heater which heats condensate whose pressure is risen by a condensate pump , a deaerator which heats and de-aerates the condensate heated by the feed water heater , a deaerator water level control valve which controls a water level of the deaerator , an extraction system which introduces the steam extracted from the turbine into the feed water heater , and an extraction valve installed in the extraction system , characterized in that the power plant comprises: an auxiliary steam introduction system which introduces auxiliary steam into the feed water heater ; an auxiliary steam control valve which is installed in the auxiliary steam introduction system and controls an amount of steam supplied to the feed water heater ; and a control device which outputs opening command signals to the deaerator water level control valve , the extraction valve , and the auxiliary steam control valve , wherein the control device controls the extraction valve in a closing direction, controls to maintain an opening of the deaerator water level control valve , and controls the auxiliary steam control valve in an opening direction in a case where a rapid load increase request is made to the power plant. an auxiliary steam introduction system which introduces auxiliary steam into the feed water heater ; an auxiliary steam control valve which is installed in the auxiliary steam introduction system and controls an amount of steam supplied to the feed water heater ; and a control device which outputs opening command signals to the deaerator water level control valve , the extraction valve , and the auxiliary steam control valve , wherein the control device controls the extraction valve in a closing direction, controls to maintain an opening of the deaerator water level control valve , and controls the auxiliary steam control valve in an opening direction in a case where a rapid load increase request is made to the power plant. <EOS>