Abstract: The control of the Wshape flame supercritical oncethrough boiler has some features, which include that the overheated steam temperature control and the coalwater ratio control are strong coupled，the furnace temperature is too high and leads severe coking，the control object of the overheated steam temperature has larger lag and longer inertia time and others. Aiming at above features, the increment function observer and state feedback control were added into the overheated steam temperature cascade PID control system of the 2×600MW unit in GongXian power plant. The practical commissioning and application show that the dynamic characteristics of the overheated steam temperature were significantly improved; and in the process of condition changing, the deviation of overheated steam temperature was controlled within the allowed range. The design scheme has better practical applicability and provides certain reference for supercritical units in steam temperature control.

Key words: W-shape flame, supercritical once-through boiler, overheated steam temperature, increment function observer, state feedback