Robust Predictive Control for Boiler-Turbine Coordinated Control System

Boiler-turbine unit is a multi-input multi-output (MIMO) nonlinear system with large time-delay and a lot of disturbances, so that conventional boiler-turbine coordinated control system (CCS) cannot achieve satisfactory performance. In this paper, we consider an output-feedback robust predictive control strategy for boiler-turbine unit affected by immeasurable bounded disturbances. This control strategy combining moving horizon estimation with robust model predictive control is finally formulated as a min-max optimization problem solved by a primal-dual interior-point method. At each sampling time, the optimization criterion is maximized over worst-case estimates of initial state and disturbance sequence and minimized over optimal control sequence. In this way, the controller can effectively reject constrained disturbances. Simulation results verify that this control strategy could provide significant robustness under common disturbances such as slow time-variation of coal low heat value and dead zone characteristics of throttle valve position.