Research On Control Method Of Coordinated Control System With Valve Nonlinear Constraints

The coordinated control system occupies a central position in the control system of the power station.The control performance of the unit coordinated control system reflects the level of automation of the unit.The control performance of the coordinated control system reflects the level of automation of the unit.In general,when the coordination system is studied,the coordination system will be simplified and approximated,including the simplification of the boiler-turbine unit and the simplification of other equipment,and this leads to a big difference between the simulation results and the actual running results.The valve is a commonly used working fluid flow control device in a power station.The valve itself has certain nonlinear characteristics,but in the process of simulation,often only a low-order inertial link is used to represent its transfer function,and its nonlinearity is ignored.In this paper,a 500 MW supercritical unit of a power plant in China is taken as the research object.The coordination system of the unit is studied.Considering the nonlinear constraints of the main steam regulating valve,the corresponding nonlinear compensator is designed,and the feasibility of the compensator is verified by simulation.Firstly,the nonlinear mathematical model of the unit is linearized.Based on the obtained unit linearization model,the decoupling controller is designed in the form of diagonal decoupling to weaken the coupling phenomenon between the model outputs;After that,use the PI controller as the controller of the whole system,and use the particle swarm algorithm to give the initial value of the controller;Then,for the nonlinearity caused by the flow characteristics of the valve,the collected valve inlet and outlet flow data are used to obtain a scattergram that reflects the flow characteristics of the valve and to fit the function relationship between the valve opening degree and the outlet flow.This functional relationship is used to correct the controller output to compensate for valve nonlinearities;Finally,the actual compensation effect of the nonlinear compensation method is verified by a wide range of power variation experiments,follow-up experiments,anti-interference experiments and robustness experiments.The research results show that the method of valve nonlinear compensation has certain significance in shortening the adjustment time of the control system and improving the stability.The method of nonlinear compensation proposed in this thesis not only has the value of theoretical research,but also has the value of engineering application.It puts forward another idea for the optimization of thermal power unit coordinated control system and plays a reference role.