Designing of a Solar Energy and Diesel Generators Hybrid Microgrid for Sustainable Agricultural Irrigation

Abstract

The increasing integration of renewable energy sources into standalone microgrids presents significant challenges in maintaining grid stability and power quality. This thesis presents a substantial enhancement to the control strategy of a Solar Photovoltaic (SPV), Battery Energy Storage (BES), and Diesel Generator (DG) based AC microgrid. The foundational work for this research established an effective energy management system using conventional Proportional-Integral (PI) and Proportional-Integral-Resonant (PIR) controllers to minimize DG runtime. However, the inherent non-linearities of microgrid components and dynamic load conditions limit the performance of these linear controllers, particularly in terms of dynamic response and harmonic suppression. This research addresses these limitations by proposing the replacement of the conventional PI/PIR controllers within the Voltage Source Converter (VSC) with an intelligent Fuzzy Logic Controller (FLC). The FLC is designed to leverage its inherent robustness, adaptability to non-linear systems, and model-free nature to provide superior dynamic performance and grid stability. By acting as an intelligent control device, the FLC addresses the critical gaps left by its linear counterparts, leading to a cascade of system-wide benefits including further reductions in DG runtime, higher penetration of renewable energy, improved overall system efficiency, and extended equipment lifespan. A comprehensive model of the microgrid was developed and simulated in the MATLAB/Simulink environment to perform a rigorous comparative analysis. The results demonstrate the clear superiority of the proposed FLC-based strategy. The FLC achieves a more rapid and stable dynamic response to load transients and, most notably, a significant reduction in the Total Harmonic Distortion (THD) of the DG set\'s voltage and current, ensuring stricter compliance with the IEEE 519 standard. The findings validate that the implementation of an FLC is a pivotal step towards creating more intelligent, efficient, and resilient standalone power systems.

Introduction

The text presents a thesis focused on improving the control performance of a standalone hybrid microgrid designed for remote and off-grid areas. The microgrid integrates Solar Photovoltaic (SPV) generation, a Battery Energy Storage System (BES), and a Diesel Generator (DG) as backup. While the hybrid architecture reduces fossil fuel dependence and emissions by prioritizing solar energy and storage, maintaining power quality and system stability under dynamic and non-linear conditions remains a challenge.

The baseline system employs an advanced energy management strategy that minimizes DG runtime, but it relies on conventional PI/PIR controllers for low-level Voltage Source Converter (VSC) control. These linear, fixed-gain controllers perform well near specific operating points but struggle with the inherent non-linearity of microgrids, leading to slower dynamic response, limited harmonic mitigation, higher Total Harmonic Distortion (THD), and indirect increases in DG usage.

To overcome these limitations, the thesis proposes replacing the PI/PIR controllers with a Mamdani-type Fuzzy Logic Controller (FLC) in the VSC current control loops. The FLC uses error and change-in-error inputs, linguistic rules, and centroid defuzzification to provide adaptive, non-linear control without requiring an exact mathematical model. This intelligent approach enhances robustness across varying operating conditions.

Simulation studies in MATLAB/Simulink compare the baseline PI/PIR strategy with the proposed FLC under identical and demanding conditions, including DG-connected mode with non-linear loads. Results demonstrate that while the PI/PIR controller meets IEEE 519 standards, the FLC achieves significantly lower THD, faster dynamic response, and improved stability.

Conclusion

This thesis embarked on the objective of enhancing the operational performance of a standalone Solar Photovoltaic (SPV), Battery Energy Storage (BES), and Diesel Generator (DG) based AC microgrid. The foundational work established a highly effective energy management system using an advanced Proportional-Integral/Proportional-Integral-Resonant (PI/PIR) controller. However, the inherent limitations of these linear controllers in handling the non-linearities and dynamic disturbances of a modern microgrid presented a clear opportunity for significant improvement, particularly in the critical areas of power quality and grid stability. The core contribution of this research was the development and integration of an intelligent Fuzzy Logic Controller (FLC) as a direct replacement for the conventional PI/PIR controllers within the Voltage Source Converter\'s (VSC) inner current control loops. To validate this extension, a comprehensive and faithful model of the entire microgrid system was meticulously constructed in the MATLAB/Simulink environment. This allowed for a rigorous and direct comparative analysis between the baseline PI/PIR strategy and the proposed FLC strategy under identical, challenging operational scenarios involving severe non-linear loads.

References

[1] G. K. Taneja, Gaurav Modi, An Improved Control Strategy to Reduce Operating Hours of DG Genset in Solar PV-BES-DG Based AC Microgrid, IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 59, NO. 3, MAY/JUNE 2023. [2] S. Singh, M. Singh, S. C. Kaushik, “A Comprehensive Review on Energy Management in Microgrids Using Rule-Based and Optimization-Based Strategies”,Journal of Modern Power Systems and Clean Energy, vol. 9, no. 2, pp. 242-257, March 2021. [3] A. Saxena, P. Kumar, I. Hussain, “A Comparative Study of PI and Fuzzy Logic Controllers for Voltage Regulation in AC Microgrids” , 2017 6th International Conference on Computer Applications In Electrical Engineering-Recent Advances (CERA), Roorkee, India, 2017, pp. 108-113 [4] N. Priyadarshi, S. Padmanaban, et al, “Fuzzy Logic Based Control for Power Quality Improvement in a Grid-Connected Microgrid”. IEEE Access, vol. 8, pp. 224989-225001, 2020

Copyright

Copyright © 2025 Salluri Santhosh, M. T. Naik. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.