Research And Simulation Of Main Steam Pressure Control System For Supercritical Once-through Boiler

Due to the high efficiency and strong adaptability of load and other prominent advantages, supercritical units should be the development trend for electric power construction of our country. As the parameter place is restricted, supercritical units must adopt the form of once-through boiler. Special water-steam flow structure, make once-through boiler has strong coupling, nonlinear characteristics, dynamic characteristics is very complicated. Main steam pressure as one of the important control parameters for unit operation, show the characterization of the balance between turbine and boiler. Feed-forward compensation is the most commonly used control methods for the main steam pressure regulation, but it is too hard for the common fixed parameter control system to meet the needs of the control system. Therefore, this paper committed to design some intelligent control system, in order to improve the effect of traditional steam pressure control system. A set of certain precision analysis model of the system is needed for the research and test of control method. But the research on the model for supercritical unit with three input and three output system model is very few. Based on the dynamic turbulence test in STAR - 90 simulation platform, a parameter model for 660MW unit in Dingzhou power plant that under the condition of full load has been recognized. Then the control characteristic of the unit is analyzed based on the model. The feed -forward compensation decoupling control system was designed and the decoupling effects were verified by simulation. After that, a kind of fuzzy self-tuning PID controller was be studied and designed, the controller can adjust controller parameters intelligently according to the system's control state, n order to achieve stable and rapid control effect. Finally, the simulation experiments show that compared to the system which using common controller, main steam pressure control system which using fuzzy self-tuning PID controller has better control characteristic.