APPLICATION OF CLASSICAL STEP RESPONSE METHOD TO EVALUATE THE PID CONTROLLER CONSTANTS FOR CONTROLLING THE CRITICAL PROCESS PARAMETERS OF A 500 MW STEAM GENERATOR IN A THERMAL POWER PLANT DURING FUEL SWITCHING

Abstract

The proportional, Integral and derivative constants of the PID controllers to control the main steam pressure of a fossil fuel fired boiler had been calculated for satisfying certain performance requirements during specified load disturbances. These constants have not been holding good when disturbances emanating from inputs to the boiler such as variations in calorific value of the coal burnt (fuel switching) in the boiler. To mitigate the negative effects of fuel switching on critical boiler parameters, an embedded controller with high gain had been proposed in the literature. In all these cases, the calculation of the controller parameters is based on tuning map concept. In this paper, the calculation of controller parameters based on classical tuning concepts has been presented. The controller parameters thus obtained and used has provided better performance characteristics during fuel switching disturbances.