Observer-Based Output Feedback Integral Control for Coal-Fired Power Plant: A Three-Time-Scale Perspective

The multivariable coal-fired power plants (CFPPs) are characterized by several interconnected nonlinear subsystems of varying time lags making the whole system stiff, and thereby attaining multitime-scale property. In this case, controls based on singular perturbation and time-scale theories provide superior results than conventional one. This brief aims to develop an integral state feedback controller with an observer using three-time-scale approach for CFPP. The integral action assures zero steady-state error, an observer determines states, and a three-time-scale technique provides flexibility to design independent subsystem controls. First, a state space model is obtained with state feedback integral action in three-time-scale form. Second, three-stage feedback control is proposed by an innovative two-time-scale separation so as to reduce design complexity and computations. Finally, an observer is constructed again by time-scale decoupling. It is then examined on the practical model of 300-MW CFPP for investigating plant behavior under various transients. In comparison, the performance of the suggested controller is found to be superior to a recently published controller.