Simulation Of Dynamic Real-time Model And Feed Water Control Of600Supercritical Once-through Boiler

The thermal power unit has higher capacity and parameter with the development ofelectric technology in recent years,600MW supercritical one-through unit graduallybecomes the crucial units of domestic coal power plants. The one-through unit’s systemis very different from the traditional drum boiler in system installation and the change ofthe working medium parameters during the running period. There is little knowledge ofthe dynamic characteristics of the supercritical one-through boiler, which brings thecorresponding problem for the design and debugging of control system. Therefore,in-depth research for the dynamic characteristics of supercritical once-through boilerand the further study for control systems which can improve the unit performance arevery significant.All the models are built based on the modular modeling method, the600MWonce-through boiler is the research object in this paper. The author establish the non-realtime capable modular and real time capable modular respectively, then carry out the stepdisturbance test, the simulation results show the dynamic characteristics under twokinds of working conditions which are75%and100%load. The results show that boththe non-real and real time capable models can describe the dynamic characteristic ofboiler accurately. The non-real time capable model has the higher accuracy, and the realtime capable model has the faster calculation speed.On the basis of the real time capable model, this paper further adds the feed watercontrol system, which plays a quite significant role in the entire unit. Through the studyof advanced control system of similar units in domestic and oversea, combining withthe practical operation of the unit, the coal-water control strategy which is based oncorrection of the intermediate point enthalpy is chosen, a strategy which taking enthalpyof slightly-superheated steam at the separator exit as the feedback signal of coal-waterratio. The simulation proves that the feed water control strategy can keep thesuperheated steam temperature in an adjustable range, and it can maintain the accuracyand rapidity of the coal-water control.The models built in this paper show the dynamic characteristics of one-throughaccurately, so the research has good engineering application value, and the feed watercontrol strategy which is used in this paper can provides some reference to other similarunits.