An Experimental Validation of Nonlinear Extended State Observer Controlled Small Hydro-PV Array and Battery Storage-Based Microgrid for Remote Areas

This paper presents a hybrid microgrid system designed for rural areas, integrating small hydro and photovoltaic (PV) arrays with battery storage to ensure uninterrupted power supply to local loads in isolated regions. A self-excited induction generator (SEIG) is employed for small hydro power generation, while power quality issues caused by nonlinear loads are addressed using the Volterra Filtered-X Least Mean Square (VFXLMS) technique. This method effectively suppresses dominant harmonic components in load currents and accurately estimates the fundamental frequency of load currents. The PV array is interconnected at the DC link of a voltage source converter (VSC) through a boost converter, while a bidirectional converter manages battery operations, facilitating efficient power management. The bidirectional converter supports the export and import of power from/to the battery, optimizing energy utilization within the microgrid. Conventional proportional-integral (PI) control has limitations in DC voltage tracking and mitigating overshoot and undershoot. To address this, a nonlinear extended state observer (NESO) is employed to mitigate disturbances. The NESO, combined with a disturbance observer, enhances the operational reliability of the microgrid. An experimental setup has been developed to validate the system’s performance under conditions of unbalanced loads and varying PV insolation levels. Note to Practitioners—The hybrid microgrid system proposed in this study offers a practical solution for addressing the energy needs of rural and isolated regions. By integrating small hydro and photovoltaic (PV) arrays with battery storage, the system ensures reliable power delivery to local loads. Practitioners working in rural electrification can benefit from the system’s ability to manage unbalanced loads and varying renewable energy sources effectively. A key feature of the proposed system is the use of a self-excited induction generator (SEIG) for small hydro power generation. This choice simplifies the system’s deployment and maintenance, making it suitable for remote areas. Additionally, the Volterra Filtered-X Least Mean Square (VFXLMS) technique effectively mitigates harmonic distortions caused by nonlinear loads, enhancing the power quality delivered to consumers. Energy management within the microgrid is streamlined through the integration of a boost converter for PV arrays and a bidirectional converter for battery control. The bidirectional converter optimizes energy utilization by facilitating power export and import, ensuring balanced energy flows during varying load and generation conditions. The study highlights the limitations of conventional proportional-integral (PI) controllers in handling dynamic disturbances. The implementation of a nonlinear extended state observer (NESO), combined with a disturbance observer, provides a robust solution for achieving precise DC voltage regulation, minimizing overshoot and undershoot, and enhancing overall system stability. This work also underscores the importance of experimental validation. The developed experimental rig demonstrates the system’s performance under real-world scenarios, such as unbalanced loads and fluctuating PV insolation, offering confidence in its practical applicability. Practitioners are encouraged to explore this hybrid microgrid design as a scalable and cost-effective approach to rural electrification, especially in areas with access to small hydro resources and solar potential. The system’s modular architecture and advanced control strategies ensure adaptability to various environmental and operational conditions.