Control Improvement Research On Superheated Steam Temperature Of The Thermal Power Plant On The Basis Of Predictive Function Control

The superheated steam temperature is one of the most important operationparameters of the thermal power plant, but also the highest temperature parameters ofthermal power plant steam system,and the control quality of the superheated steamtemperature will directly affect the safety and efficiency of thermal power plants. If thetemperature is too high, there may be damage to superheater materials, while thermalexpansion within the turbine will make a serious threat to operation security; if thetemperature is too low, the efficiency of the system will decrease, while excessivehumidity will be caused to the last stage steam turbine, causing leaf loss. Because of thelong large-scale power plant superheater tube and the large heat capacity of the tubewall made the large inertia and hysteresis steam temperature,therefore superheatedsteam temperature control is the difficulty of thermal control.Firstly, the paper analyzes the dynamic characteristics and static characteristics ofthe superheated steam temperature object, studies the the steam temperaturecharacteristics’ different temperature characteristics under different loads: When the unitat high load, the steam temperature characteristics will tend to be convection, high heattransfer efficiency,large inertia, short steam flow disturbance regulation time, largeovershoot; When the unit at low load, the steam temperature characteristics will tend toradiation, less heat transfer efficiency, small inertia, long regulation time for the steamflow disturbance, small overshoot.Secondly,the paper analyzes the defect of the predictive functional control systemin overcoming the steam flow disturbance.That’s to say,the anti-interference ability ofthe system is poor in the case of model mismatch. The paper analyzes the characteristicsof steam temperature and points out ways to reduce the degree of model mismatch byusing of dynamic models.Thirdly, by collecting field data and using system identification to strike the steamflow-superheated steam temperature model in different conditions.By analyzing thesteam flow disturbance model under different conditions, we obtained variation ofcoefficient of the model,and then through fitting the monotonous coefficient, we gotrepresentation of the dynamic disturbance model.Finally,the paper simulated the dynamic model during the resolving the effect of model mismatch problems in the prediction function of the superheated steamtemperature control.And,we found that dynamic model can be a good solution to solvethe problem of model mismatch and improve the dynamic performance of the system. Itturns out making use of dynamic forecasting model to optimize the control system ofthe superheated steam temperature is reasonable. However,it is still a long way to gofrom theory to application.It’s also need further work to make the optimization appliedto superheated steam temperature control system of actual power plant.