Control of desalination plants using sliding mode scheme with state observer

• Published in: Aqua (London, England) Vol. 70; no. 6; pp. 783 - 796
• Main Authors: Bui Duc Hong Phuc, Sam-Sang You, Hwan-Seong, Kim, Sang-Do, Lee
• Format: Journal Article
• Language: English
• Published: Oxford IWA Publishing 01-09-2021
• Subjects: Algorithms; Brackish water; Climate change; Control; Control algorithms; Control stability; Control systems; Control theory; Controllers; Desalination; Desalination plants; Design; Membranes; Monitoring systems; Neural networks; plant automation; Process controls; real-time control; Reverse osmosis; Robust control; Sensors; Sliding mode control; Slumping; State estimation; State observers; Sustainability; Uncertainty; Water desalting; Water flow; Water quality; water treatment
• ISSN: 1606-9935; 2709-8028; 2709-8036
• DOI: 10.2166/aqua.2021.035

This paper deals with real-time control with observer to manipulate desalination plants as well as to monitor system states for smart operations. The controller plays an important role in achieving stabilization of reverse osmosis (RO) systems to guarantee the desired water product and concentration. The super-twisting (STW) sliding mode control (SMC) algorithm guarantees performance while reducing chattering. Supposing that all the state variables are not available by sensors, the observer is implemented to provide state estimation. Since smart operations depend on control algorithm and sensor availability, the proposed strategy provides robustness to ensure the water productivity even under uncertainties or under failure of sensors. The robustness is guaranteed by active controller where 80% of disturbance is eliminated in product water flow and that of product water quality is approximately 95%. As well, the state observer can produce precise predictions of the unmeasured states. Sliding mode control with observer provides the system with stability, while assuring better performances against uncertainties. Finally, the active controller with state estimator can guarantee a robust control strategy and monitoring system to extend the life of the filters and membranes, while ensuring sustainability. This control strategy is highly recommended for smart operations of desalination plants.