K Salitha, H.A. Vidya, J. Ramprabhakar
For clean energy goals, energy independence, resilience, and efficient use of distributed energy resources, renewable energy sources are often connected to microgrids. Grid-Forming Inverters (GFIs) are one of the major transformative solutions for amplifying the stability and resilience of power systems, particularly in decentralized and islanded microgrids. Unlike conventional grid-following inverters, GFIs can independently regulate voltage and frequency, thus forming the grid in the absence of a central utility. This capability makes them essential for integrating Renewable Energy Sources (RES) like solar and wind, especially in areas where traditional synchronous generation is minimal or absent. The development of advanced power electronic converters—such as Voltage Source Inverters (VSIs), Current Source Inverters (CSIs), and multilevel topologies—has been instrumental in supporting grid-forming functionalities with improved dynamic performance, efficiency, and fault tolerance. As the complexity of distributed generation networks increases, hybrid architectures combining grid-forming and grid-following inverters are gaining attention. These architectures ensure both power-sharing flexibility and system stability by leveraging the strengths of each inverter type. Additionally, advancements in wide-bandgap semiconductor technologies (SiC, GaN) have enabled faster switching speeds, higher power densities, and reduced losses, which are crucial for high-performance hybrid systems. That makes the world evolve into a new era of small-scale distribution from the static grid entity. Power converters are the main components in the microgrid. To meet evolving grid codes and ensure compatibility with existing infrastructure, control strategies are becoming more intelligent and adaptive. Integration of communication-assisted control, decentralized decision-making, and artificial intelligence (AI) enables predictive, real-time optimization of hybrid inverter networks. Moreover, hierarchical control frameworks—comprising primary, secondary, and tertiary levels—are being refined to manage both fast transient dynamics and long-term system objectives. These advancements collectively mark a significant shift from conventional passive grid support to active, resilient, and autonomous energy systems led by next-generation converter technologies. This paper aims to outline basic converter topologies and their advancements. The advancement of the converter reveals the idea of proper converter installation in the microgrid applications. The benefits of each of the proposed converters are explained. The main factors described about each are efficiency, system volume, and output voltage ripple. Also highlighted are the main power quality issues, power converter parameter requirements, and the importance of power converters in the grid system. This study presents a comprehensive analysis of hierarchical control architectures in microgrid systems encompassing primary, secondary, and tertiary control levels. Key control strategies are discussed along with the system configuration.