Series-Cascaded AC Microgrids: An Inclusive Review of Architectures and Control Methodologies

The modern utility grid is transitioning from a centralized to a distributed structure, facilitated by integrating distributed generation sources (DGs) and loads. Microgrids (MGs) have emerged as a key solution, with different topologies such as parallel AC microgrids, series-cascaded AC microgrids (SC-ACMGs), and series-parallel ACMGs, each offering distinct advantages for specific applications. Parallel ACMGs provide fault tolerance and well-established protection schemes, making them widely adopted in industrial and urban power grids. Meanwhile, SC-ACMGs offer modular scalability and efficient voltage stacking, making them suitable for renewable energy sources (RESs) integration, battery energy storage, off-grid electrification, and electric vehicle charging infrastructure. Series-parallel ACMGs combine features of both but introduce additional control complexity. With increasing interest in SC-ACMGs for applications requiring direct voltage stacking and reduced power conversion stages, this paper provides an inclusive review of SC-ACMG architectures and their control methodologies. While SC-ACMGs enable cost-effective and flexible control, they face challenges such as power sharing, frequency synchronization, and voltage regulation, particularly with higher penetration of RESs. This paper explores different SC-SCMG configurations, technical challenges, and control methodologies, providing a comparative analysis of existing methodologies. Furthermore, it identifies research gaps, future trends, and technical barriers to large-scale deployment while suggesting potential solutions. Finally, it discusses emerging technologies to enhance SC-ACMG integration with smart grid features, serving as a valuable resource and roadmap for researchers working on next-generation power systems.