Towards an improved gain scheduling predictive control strategy for a solar thermal power plant

This paper improves a recently proposed gain scheduling predictive control strategy for the ACUREX distributed solar collector field at the Plataforma Solar de Almería, in south-east Spain. Measured disturbances are an integral part of the plant and while simple classical, series and parallel, feedforward approaches have been proposed and used extensively in the literature, the proposed approach incorporates a feedforward systematically into the predictive control strategy by including the effects of the measured disturbances of the ACUREX plant into the predictions of future outputs. Models of the measured disturbances are estimated around a family of operating points directly from input-output data and using a subspace identification method while taking into account the frequency response of the plant. Input-output data are obtained from a validated nonlinear simulation model of the plant rather than the plant itself. The nonlinear simulation model is validated here against measured data obtained from the ACUREX plant and the effectiveness of the proposed control approach is evaluated in the same nonlinear simulation environment. The paper also considers related issues like the significance of sufficient modelling of the measured disturbances of the ACUREX plant and the impact of incorporating the expected future behaviour of a measured disturbance along a given prediction horizon, a theme which has received little attention in the literature.