Improving Temperature Tracking Control for Solar Collector Fields Based on Reference Feedforward

Abstract

Improving temperature reference tracking in solar collector fields is essential for enhancing the performance of solar thermal plants. Conventional control strategies are usually employed as static reference feedforwards (FFs) to reduce rise time when reference changes occur. Nevertheless, strict performance requirements may demand precise control behavior that classical reference FFs cannot deliver. Therefore, from theoretical analysis, this work proposes two different control strategies based on reference FF structure to accomplish a low rise time and avoid producing overshoot for temperature reference tracking, namely, a lead–lag and a nonlinear reference FF. The structures are studied for suitable implementation, assuming an adaptive control framework to keep the same control performance under different operating conditions. Simulation experiments are developed to investigate and compare the proposed strategies with the conventional static FF with and without a reference filter. Furthermore, the proposed strategies are successfully tested in an actual solar plant AQUASOL-II, located in the Plataforma Solar de Almería (PSA), Almería, Spain. The promising results have concluded that the lead–lag and nonlinear reference FF associated with the adaptive structure have attended the proposed control requirements of low rise time and no overshoot. Moreover, the results have demonstrated the compromise between the lead–lag and the nonlinear controller, where the final choice should be made as a tradeoff between performance and control effort.