In this paper, we detail the design, analysis, and implementation of a highly distributed off-grid solar photovoltaic dc microgrid architecture suitable for rural electrification in developing countries. The proposed architecture is superior in comparison with existing architectures for rural electrification because of its 1) generation and storage scalability, 2) higher distribution efficiency (because of distributed generation and distributed storage for lower line losses), 3) ability to provide power for larger communal loads without the requirement for large, dedicated generation by extracting the benefit of usage diversity, and 4) localized control by using the hysteresis-based voltage droop method, thus eliminating the need for a central controller. The proposed microgrid architecture consists of several nanogrids capable of the self-sustained generation, storage, and bidirectional flow of power within the microgrid. Bidirectional power flow and distributed voltage droop control are implemented through the duty cycle control of a modified flyback converter. A detailed analysis in terms of power flow, loss, and system efficiency was conducted by using the Newton-Raphson method modified for dc power flow at varying distribution voltages, conductor sizes, and schemes of interconnection among the contributing nanogrids. A scaled-down version of the proposed architecture with various power sharing scenarios was also implemented on hardware, and yielded satisfactory results.

DC microgrids built through a bottom-up approach are becoming popular for swarm electrification due to their scalability and resource-sharing capabilities. However, they typically require sophisticated control techniques involving communication among the distributed resources for stable and coordinated operation. In this work, we present a communication-less strategy for the decentralized control of a photovoltaic (PV)/battery-based highly distributed dc microgrid. The architecture consists of clusters of nanogrids (households), where each nanogrid can work independently along with provisions of sharing resources with the community. An adaptive I-V droop method is used, which relies on local measurements of state of charge and dc bus voltage for the coordinated power sharing among the contributing nanogrids. PV generation capability of individual nanogrids is synchronized with the grid stability conditions through a local controller, which may shift its modes of operation between maximum power point tracking mode and current control mode. The distributed architecture with the proposed decentralized control scheme enables 1) scalability and modularity in the structure, 2) higher distribution efficiency, and 3) communication-less, yet coordinated resource sharing. The efficacy of the proposed control scheme is validated for various possible power-sharing scenarios using simulations on MATLAB/Simulink and hardware-in-the-loop facilities at the Microgrid Laboratory, Aalborg University.

The protection of AC microgrids (MGs) is an issue of paramount importance to ensure their reliable and safe operation. Designing reliable protection mechanism, however, is not a trivial task, as many practical issues need to be considered. The operation mode of MGs, which can be grid-connected or islanded, employed control strategy and practical limitations of the power electronic converters that are utilized to interface renewable energy sources and the grid, are some of the practical constraints that make fault detection, classification, and coordination in MGs different from legacy grid protection. This article aims to present the state-of-the-art of the latest research and developments, including the challenges and issues in the field of AC MG protection. A broad overview of the available fault detection, fault classification, and fault location techniques for AC MG protection and coordination are presented. Moreover, the available methods are classified, and their advantages and disadvantages are discussed.

Low-voltage, low-power solar photovoltaic (PV) based DC microgrids are becoming very popular in non-electrified regions of developing countries due to a) lower upfront costs compared to utility grid alternatives and b) limited power needs of rural occupants. The optimal planning of distribution architecture along with sizing of various system components such as solar panels, batteries and distribution conductors is essential for minimizing the system cost and enhance its utilization. In this work, we develop a framework for optimal planning and design of low-power low-voltage DC microgrids for minimum upfront cost. The analysis is based on a) region-specific irradiance and temperature profiles, b) constraints in storage and distributions, c) distribution loss analysis and d) optimum component sizing (storage, conductor and PV panel) requirements based upon an energy balance model for a 24-hr operation. We further analyze the merits of tailoring distribution architecture for maximizing the system utility in the planning of future microgrid deployments.

There is a worldwide focus on the electrification of developing regions, as is evident from the sustainable development goals (SDGs) of the United Nations. In particular, the aim of SDG 7 is to ensure universal access to affordable, reliable, sustainable, and modern energy services for all by 2030. Because of these sustained efforts, more than 1 billion people worldwide have gained access to electricity since 2000. During this course, the electrification architecture of developing regions has taken different forms, ranging from extensive utility grid extensions to limited off-grid solutions. Off-grid solutions generally offer cost-effective and lower up-front cost alternatives in comparison to utility grid extensions and are deemed more suitable for developing economies. In developing economies, these off-grid electrification solutions have evolved from individual solar home-based systems to community-based microgrids in pursuit of achieving higher efficiency and reliability on a village scale. Community grids responsible for the electrification of developing regions are further categorized based on architecture, type of generation, and mode distribution.