Practical disturbance rejection control for boiler-turbine unit with input constraints

Abstract

With the increase of renewable sources participating into the power grid, the traditional thermal power generation is responsible for the frequent power regulation where the disturbance rejection ability should be enhanced during the operation. The boiler-turbine unit is a non-strictly proper multivariable plant with uncertainties, external disturbances and hard constraints, which make the conventional control strategy hard to meet the operating requirement. To this end, an advanced control strategy of generalized active disturbance rejection control (GADRC) is proposed in this paper, consisting of multivariable extended state observer (MESO) and anti-windup compensator. A simple transformation approach is proposed, which can convert the output disturbances involving the feedthrough item into the input lumped disturbances, so that their impact can be estimated by the MESO and compensated by the proposed GADRC. In addition to this, a setpoint filter is developed in the control structure to remove the tracking offset caused by the unknown disturbances and a novel anti-windup strategy is presented to handle the input saturation problem and alleviate the resulting fuel waste issue. The robust stabilities of the proposed GADRC including feedback control and anti-windup control are guaranteed using frequency domain method and Circle criterion, respectively. Simulation studies compared with other methods demonstrate the effectiveness of the proposed control strategy on the boiler-turbine unit, especially in complex cases of external disturbance and model-plant mismatches.