pH control in raceway photobioreactors using Extremum Seeking with out-of-bandwidth dither and phase shift compensation Abstract
DOI:
https://doi.org/10.17979/ja-cea.2025.46.12190Keywords:
ESC, Microalgae, Feedfoward, Measurable disturbancesAbstract
This work presents the design and implementation of an Extremum Seeking Control (ESC) approach applied to pH regulation in a microalgae raceway. The dynamics of the system presents a variable and very slow time constant, which prevents the dither signal from being located within the effective bandwidth of the system. Therefore, the dither is placed outside the effective bandwidth, generating attenuation and phase shift in the modulated signal. To counteract this effect, the cutoff frequency of a high-pass filter in the demodulation stage is adjusted so that the total phase shift - resulting from the sum of the system and filter phase shifts - is approximately in the centre of the expected range. This strategy improves the robustness and stability of the ESC to system dynamic variations. In addition, a feedforward action is incorporated to compensate for measurable disturbances caused by incident radiation.
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Copyright (c) 2025 Jose González-Hernández, Laurent Dewasme, Alain Vande Wouwer, José Luis Guzmán, José Carlos Moreno
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