H∞ control for a boiler-turbine unit

A loop-shaping H_∞ controller is designed for a nonlinear multivariable boiler-turbine system. Simulations show that the designed controller has good tracking, disturbance rejection properties, and robustness against the variations of the operation points due to the plant nonlinearity. In order to implement the complex H_∞ controller, we propose a method to reduce it to a multivariable PID controller. The final simplified controller is composed of three main channel PI controllers plus one off-channel PI controller. It reveals the underlying structure of the designed controller and that of the overall boiler-turbine control system. Simulation results show that it maintains the good properties of the original controller