The control quality of the intermediate point enthalpy of supercritical units directly affects the control quality of water-fuel ratio and main-steam temperature of the once-through boilers

it also relates to economic and stable operation of the supercritical units. In order to realize high quality control for the intermediate point enthalpy

this paper proposed a fuzzy control scheme for intermediate point enthalpy of the feed-water temperature

which overcomes the contradiction between the quick response of the intermediate point enthalpy control and the stability of separation interface of the separator. In this method

a mechanism model of the once-through boiler in a 600 MW supercritical unit is adopted as the control object

the feed-water temperature is introduced into the intermediate point enthalpy control system model

and two widely used control schemes(modifying feed-water quantity and modifying feed-coal quantity) for water-coal ratio are combined via fuzzy control. The simulation results show that

the improved intermediate point enthalpy control system for feed-water temperature has advantages of both rapid response in feed-water quantity control and stability in feed-coal quantity control

which effectively considers both the economy and safety during the regulation and gains satisfied control effect.