| Drum level is one of essential parameter of large-scale thermal power plant units . Because of complication of feed-water system, the effect of full range feed-water control system does not often be satisfied when power unit is in difficult situation, more and more large power plants propose the better design for the existing full range feed-water control system to improve control effect. The author achieves better design for full range feed-water control system which is based on the project of " feed-water control system improvement of No .2 unit" that is sponsored by HuNan YiYang power plant .The dissertation sententiously discusses the problems of full range feed-water control in low load condition which basing on analysis of feed-water characters. A better design is completed based on the decoupling theory, when the coupling relationship of drum level control and feed-water control is concerned. At the same time, a automatic switch design for feed-water modulate valves is finished .Another emphasis of the dissertation is the design of feed-water pump coordinated control system, which based on three-element control system with the intention to elevate feed-water control level in emergency. It integrates advantages of feed-water control with coordinated control , which not only makes use of the advantages of three-element control system, but also automatically switch to feed-water pump coordinated control when feed-water pump is in fault.After installation and debugging of the expert system in the lab, it operates stably and reliably, and can implement the purpose of improving feed-water control both in normal and in fault. It is proved that the expert system had highly practical value. |
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