Super-twisting-based sliding mode control of drum boiler energy conversion systems

A drum boiler is the most critical part of power generation plants. The control of a highly nonlinear, multiple input and multiple output drum boiler system (DBS) is a challenging task. In this work super-twisting sliding mode controllers (STSMCs) are designed for the control-oriented model of the DBS, which maintain a desired water level and pressure of the drum. The unknown state of the DBS required for the control design is estimated using a gain-scheduled Utkin observer (GSUO). A rigorous mathematical analysis is also included to show that the closed-loop system is locally stable. The simulation results show that the closed-loop system yields the required performance even in the presence of parametric uncertainty, process and measurement noises, and external disturbance. To make a fair comparison, a quantitative analysis is also carried out for STSMC and PI controllers. Both controllers consume similar control energy, but STSMC shows better tracking performance.