Modeling And Control Of Supercritical Unit Combustion Control System In Thermal Power Plant

The supercritical unit combustion control system in thermal power plant is an energy conversion system that transforms the heat generated by burning coal to mechanical energy. It provides energy source for the whole thermal power plant system. So it is necessary to study combustion control system deeply in order to improve operational efficiency of the whole supercritical unit in thermal power plant.In this paper, the supercritical unit combustion control system in thermal power plant is studied, the correlative study mainly focused on the two aspects:object modeling and control arithmetic.Designing of combustion control system must be based on a complete and accurate mathematical model. An accurate mathematical model can reflect exact parameters of thermal equipments and the dynamic response process. Also it can help engineers understand dynamic characteristics of the thermal system. This paper analyzes the mechanism of combustion control system in detail. Firstly, four subsystems of combustion control system are described in the form of differential equations. The four subsystems contain coal mill pulverizing system, main steam pressure control system, flue gas oxygen content control system and furnace pressure control system. Secondly based on the relationship between inputs and outputs all the subsystems are cascaded to build the entire mechanism model of the supercritical unit combustion control system. Then, to verify the correctness of the established model, three input variables are given with step disturbance separately to observe and research the dynamic response characteristics of three output variables respectively in the situation of four different working conditions (100%load,75%load,50%load and35%load). The input variables are consisted of feed coal quantity, supplied air volume and quoted air content and the output variables are formed by main steam pressure, furnace pressure and flue gas oxygen content.For the nonlinear, large-time-delay, strong-coupling and multi-variable characteristics of the supercritical unit combustion control system and other external interference of the scene, this paper designs a fuzzy self-tuning PID controller. In order to achieve stable and rapid control effect, the controller can adjust controller parameters intelligently according to the system’s state. Finally, the simulation experiments show that compared to the traditional controller the fuzzy self-tuning PID controller has a better control characteristic.