Multi-model based IMC design for steam temperature system of thermal power plant

IMC-PID(internal model control-proportional plus integral plus derivative) cascade control strategy is presented based on multiple models control theory, which keeps the merit of cascade control system as well as multiple models control. Fixed parameters PID control is used in inner loop in order to eliminate disturbances, then the inner loop and main inertia plant are regarded as the generalized object to be controlled by IMC method. FOPDT (First Order Plus Dead Time) model is used to describe the internal models for IMC, this avoids the problem of realization of a high order controller. The method of scheduling among the local models is according to power load that is the primary factor. Smoothiing switch is realized by using fuzzy weighting function. The simulation results demonstrate that the strategy proposed is well suited to nonlinear multi-model and time-various systems such as superheated steam temperature plant.