Minigrid integration planning (MGIP) for loss reduction and voltage profile improvement beyond energy access in developing countries

To improve access to electricity and achieve Sustainable Development Goal 7 (SDG7), a mixture of grid extension and off-grid systems, like minigrids, are under deployment in many developing countries, including sub-Saharan Africa (SSA). Beyond meeting energy access goals, the main grid will continue expanding and eventually converge and integrate with minigrids. Such integration has the potential to address network losses and low quality of supply in developing countries, similar to how the optimal placement and sizing of distributed energy resources (DERs) has impacted distribution networks in the global north. However, unlike in the DER integration, there is no suitable planning methodology for maximizing the benefits of grid integration of formerly autonomous minigrids in developing countries. This paper proposes a minigrid integration planning (MGIP) methodology that ensures loss reduction and voltage improvement in post-energy access networks in developing countries. The planning problem is formulated as a mixed-integer non-linear problem (MINLP) and is solved using a Genetic Algorithm (GA). The paper demonstrates MGIP's ability to ensure loss reduction and voltage profile improvement by identifying optimal points of grid infeed into formerly autonomous minigrids. It also shows MGIP's flexibility to be applicable in a basic case of integrating a single minigrid and an advanced case of integrating a cluster of minigrids. The results show that using the MGIP approach can significantly reduce losses (by up to 65% as observed in some scenarios of the reported case studies) and improve voltage profile through the grid integration of formerly autonomous minigrids in the post-SDG7 electrical networks in developing countries

Voltage stability of power systems with renewable-energy inverter-based generators: A review

© 2021 by the authors. The main purpose of developing microgrids (MGs) is to facilitate the integration of renewable energy sources (RESs) into the power grid. RESs are normally connected to the grid via power electronic inverters. As various types of RESs are increasingly being connected to the electrical power grid, power systems of the near future will have more inverter-based generators (IBGs) instead of synchronous machines. Since IBGs have significant differences in their characteristics compared to synchronous generators (SGs), particularly concerning their inertia and capability to provide reactive power, their impacts on the system dynamics are different compared to SGs. In particular, system stability analysis will require new approaches. As such, research is currently being conducted on the stability of power systems with the inclusion of IBGs. This review article is intended to be a preface to the Special Issue on Voltage Stability of Microgrids in Power Systems. It presents a comprehensive review of the literature on voltage stability of power systems with a relatively high percentage of IBGs in the generation mix of the system. As the research is developing rapidly in this field, it is understood that by the time that this article is published, and further in the future, there will be many more new developments in this area. Certainly, other articles in this special issue will highlight some other important aspects of the voltage stability of microgrids