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Research Of Unit Plant Simplified Nonlinearity Dynamic Model

Posted on:2006-11-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:L TianFull Text:PDF
GTID:1102360152999995Subject:Thermal Engineering
Abstract/Summary:PDF Full Text Request
Lots of power plant faced the problem of coordinated control system optimization. The correlative study mainly focused on the two aspects: object modeling and control arithmetic. Constructing the unit load-pressure object model and thoroughly analyzing the characteristic of the model are the basic of the study. The study direction of this his paper is that constructing current most far-ranging unit plant model. The unit plant is 300–600MW,direct firing pulverizing system,subcritical pressure,first medium reheating,natural circulation drum boiler and condensing steam turbine unit plant. And the model is load-pressure simplified nonlinearity dynamic model on the 50%-100% load scope without infusing oil to assist combustion. The model in this paper is the basis of CCS design. The modeling process include mechanism modeling,model simplifying,parameters confirming,experiment validating and characteristic analyzing. The main task of this paper include as following: Studying the characteristic of every members of unit plant the model is simplified reasonably, then according to basic substance balance and energy balance every members mechanism model are construct. Nearby the unit running parameter the model are simplified and fitted, then the analytic model expression ware got. There are three same type and different capacity units, DaQi 330MW,ShenTou 500MW and PaShan 660MW. On the three units the experiments of fuel disturbance and turbine valve disturbance on multi load-pressure running point are made. Comparing the model and units running data the model veracity is validated. And a set effectively acquiring model parameters method is summarized. On the basic of existing model the pulverizing process and the characteristic of superheater differential pressure were analyzed. The pulverizing dynamic and water wall dynamic are united and were simplified to be a one-order inertia plus pure lag process. The order of model was depressed in the precondition of reflecting the main dynamic of unit. The steam is decalescence and swelling process in the superheater pipeline, and there is attemperation water sprayed. Revising the nonlinearity of the differential pressure and the flow, and the main steam flow was replaced by boiler decalescence to construct model. The difference between this model and ?str?m model were analyzed, then the rule was presented that 9/8 power of the pressure in ?str?m model decreased with pressure increasing and will become 1. On the basic of mechanism analysis, combining disturbance experiment and large running statistical data, the rule of the main parameters of nonlinear model changing with running point was gained. That is fuel instruction gain increased with unit load increasing. Boiler lumped storage coefficient decreased with drum pressure increasing. Pulverizing dynamic inertia time change randomly on a big scope. Using the conclusions to revise the model can reflect the practical thing of the unit more truly. Through linearizing the nonlinear model the linear model on the different load-pressure running point are gained. The nonlinearity of the model can translate into the characteristic that model parameters changing with time. So we can analyze the system with traditional method. The linear transfer function includes input variable. The representation is that the object gain and inertia change with the different running point. The mathematical description is given in this paper, and through the disturbance experiment of 330MW unit the correctness of the model is validated. Using the model the difficulty of the current CCS design are analyzed, the merit and shortage of some theoretical method are discussed. Some engineering applied methods, such as: decoupling design,PID parameters robust tune,heat value emendation and water of condensation throttle are analyzed.
Keywords/Search Tags:Unit plant, Dynamic model, Nonlinearity, Experiment analysis, Turbine and boiler Coordinated Control System
PDF Full Text Request
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