| The design trend of thermal power plant is to update system capacity and parameter. For the purpose of the secure and economic running of the power plant, the parameters of water and steam of thermal system should be controlled more strictly. Since the chemical dosing control system of fossil power plant is characterized by nonlinearity, long time lag and variation with time, satisfying control effect can not be achieved with traditional control methods. Therefore, fuzzy control theory is introduced in order to increase the robustness and self-adaptability of the chemical dosing control system in the power plant and fuzzy control system of dosing is designed in this paper.Firstly, this paper analyzes the dynamic performance of some general control schemes for time-delay system, indicates that robustness and self-adaptability of those control schemes are insufficiency. Secondly, the fundamental principles and design rules of fuzzy control are described. Idea which combines the fuzzy control with PID control is proposed, and an adaptive fuzzy-PID control model has been designed. The dynamic performance of fuzzy control and self-tuning fuzzy PID to chemical dosing system is studied by simulation. Simulation results show that the control effect by this strategy is superior to that of normal PID cascade control. It is featured by strong robustness and self-adaptability, and can readily accommodate itself to the object's parameter variations. In the end , we designed the variable frequency fuzzy control system of dosing for certain power plant feed water .The methods of operate , design software and hardware , approaches of control basing on LabVIEW and communication modes of DDE between LabVIEW and configuration software are introduced in this paper. The running results showed that the controlling system worked well and gained satisfied effect.
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