Modeling And Control Of Supercritical Unit Coordinated Control System

In recent years, supercritical units have already become thermal power units that China mainly built,and the main direction of the future development of thermal power plants. Supercritical units play an extremely important role in maintaining security and stability of the power industry. At the same time, dynamic modeling of ultra-supercritical units is the basicof the design and performance research of control system. Therefore, modeling and control of large-scale unit are especially urgent.For modeling, the key lies in whether the model is suitable for the real-time simulationand fully reflect the system dynamic characteristics. This thesis takes a1000MW supercritical generating unit for the study. Based on mechanism analysis and modeling simplification, the boiler is divided into four parts-economizer, water wall, steam separator and superheater.During the process of modeling, the positions ofphase transition points are taken as independent variables. Itsuccessfully resolves problems exist in the unit during dynamicsimulation under supercritical conditions. The derivative termsin the right of secondary modeling equations are eliminated byproper mathematical processing, therefore, the stability ofnumerical integration is improved. Furthermore,turbine is divided according to the stage groups of modeling. Turbine modelis established by using Friuli Greig formula. The dynamiccharacteristics of the unit are analyzed after simulation atin different conditions.After modeling of ultra-supercritical unit, this thesis starts to study applications of the new intelligent control to coordinated control system.Traditional PID controller is no longer suitable forcoordinated control system with nonlinear and time-varying. In order to improve the control performance system, this thesis presents a fuzzy PID controller. Traditional PID control well integrats withthe simplicity flexibility and robustness of fuzzy control, usesin supercritical unit coordinated control system. comparing experiment results ofFuzzy PID control and conventional PID control proves the superiority of fuzzy PID.