Research On Method Of Feed Water Control For USC Unit

Once-through boiler is a key feature of the ultra-supercritical unit, the control object of the control system has character of multiple-input multiple-output, nonlinear, strong coupling, varying parameters and model uncertainty and so on . Compared to sub-critical unit uses the drum boiler, with the lack of a buffer drum part, Once-through boiler feed water from liquid into vapor instantaneously, with no fixed boundaries, the main steam pressure and temperature are more sensitive to the water fluctuations, which increase the difficulty of feed water control.Feed water control system is a subsystem of the ultra-supercritical unit control system, Once-through boiler feed water control is base on the water to coal ratio, while there is also the correction link, the correction signal mainly including intermediate point temperature and intermediate point enthalpy. Stable conditions, ensure the water to coal ratio can be achieved good feed water control, but when conditions have changed or the occurrence of a change in the external input, the water to coal ratio feedback signal fluctuations which will influence the water to coal ratio's adjustment, seriously will cause water to coal ratio imbalance, feed water control failure.Firstly this article analyzes the static and dynamic characteristics of boiler, introduces the main tasks of boiler feed water control and the feed water control strategy. Then, according to the impact of coupling characteristics of Once-through boiler on feed water control system, a fuzzy neural network decoupling control method is proposed, which is a combination of fuzzy self-tuning PID control algorithm and fuzzy neural network decoupling method of dispersion. Finally with the Beijiang power plant first unit as the study object, according to the data of power generation, have established the mathematical model about the boiler feed water control system, the decoupling control method is applied to feed water control system for simulation. The results of simulation show that the decoupling control method is effective to regulate and have a satisfactory control quality.