Control System for pH in Raceway Photobioreactors Based on Wiener Models

Abstract

This paper describes a model-based control approach for the pH regulation in raceway photobioreactors. The pH variable is the most important one in the photosynthesis rate and it must be controlled within an specific range. The microalgae system is a very complex process that makes difficult to obtain simple models for control purposes. Usually, first-order models are used to describe the pH dynamics in the system and to design control algorithms. However, sometimes more complex models are required to capture the dynamics of the system and to cope with a wider operating range. For that reason, in this work, a Wiener model is presented for the pH variable looking for a trade-off between model accuracy and complexity, and where linear and nonlinear dynamics are combined. Afterwards, this model is used in a model-based control approach that allows to decouple the linear and nonlinear terms. The control scheme is based on a PID controller and a robust filter. Simulation results will show the promising behaviour of the proposed control solution.