Maintaining of actuators and final control elements modeling in a steam generating unit control system

Steam generating unit automation control system is a complex system with many sources of nonlinearities. There are two main types of nonlinearities in a steam generating unit automation control system. First, nonlinearity caused by a control object nonstationarity due to changes of operation modes and changes of object parameters with time. Second, nonlinearities caused by control system elements. Analysis of nonlinearities in steam generating unit automatic control system has been done. Attention is focused on the problem of modelling the actuators and final control element in automatic control systems. Models of saturation, relay with dead zone, backlash, viscous friction and dry friction have been studied. The available models taking into account dry friction data have been analyzed and recommendations as to applying them have been made. Operating data from the Power Block №4 automation control system of the Trypilska thermal power station have been processed. The steam generation unit control parameters of steam and water circuits for the four lines (A, B, V, G) were examined. They are temperature and pressure of steam and water in different points of steam and water circuits and the controller output signals. The relationship of a controlled parameter and time and the relationship of a controlled parameter and the controller output have been examined. Some control contours that may suffer from nonlinearity in an actuator or in a final control element were identified