A smart single stage solar battery driven desalination system with hybrid MPPT and optimal control for brackish water treatment

Reverse Osmosis (RO) desalination systems powered by renewable energy provide a practical solution for fresh drinking water in remote off-grid communities. However, RO desalination is an energy-intensive process that requires a stable and efficient power supply. This paper presents a high-performance, single-stage PV-RO desalination system with battery storage. A SHO-P&O MPPT algorithm optimizes PV power extraction, minimizes voltage fluctuations and ensures stable operation under fluctuating solar conditions. To enhance system efficiency, a Quasi-Z Source Inverter (QZSI) is integrated to improve energy conversion, eliminating the need for a separate DC-DC boost stage. Additionally, the RO system is modeled as a Two-Input-Two-Output (TITO) system, where precise regulation of the permeate flow rate and product water salinity is essential for maintaining water quality. To achieve this, a Linear Quadratic Regulator (LQR) is implemented, effectively minimizing transient errors, reducing settling time, and enhancing system stability. Furthermore, comparative analysis demonstrates that the SHO-P&O MPPT outperforms conventional P&O and standalone SHO methods, achieving 99.9% efficiency with reduced oscillations and faster tracking of MPP. Similarly, the LQR controller exhibits superior performance with a settling time reduction and an overshoot of 2%, outperforming conventional PID, FOPID and SMC strategies, which exhibit higher overshoot and longer settling times. HIL validation using the dSPACE DS1104 platform confirms the effectiveness of the proposed system in ensuring stable and energy-efficient desalination under dynamic environmental conditions.