A review on the suitability of virtual inertia strategies for the next generation of low-inertia power systems

• Conclusion The growing integration of renewable energy sources (RES) has significantly reduced the inertia of modern power systems, leading to higher frequency deviations and increased stability concerns. To address these challenges, virtual inertia (VI) control has emerged as a promising solution for improving frequency response and overall grid stability. • This paper has provided a comprehensive and structured review of VI control strategies and their implementation across multiple RES technologies. It specifically addresses two key research gaps identified in the literature: 1) the lack of a unified classification framework for VI strategies, which has led to conceptual ambiguity between grid-forming (GFM) and grid-following (GFL) controls, and 2) the limited scope of previous studies that focused only on one or a few VI control technologies without cross-technology comparison. • To overcome these gaps, this study proposes a new classification framework (illustrated in Fig. 4 ) that distinctly differentiates between the Virtual Synchronous Machine (VSM), Virtual Synchronous Generator (VSG), and Synchronverter concepts, while emphasizing both aspects of inertia provision and inertia emulation. Based on this framework, a systematic analysis and comparison were conducted across electrolyzers, electric vehicles (EVs), battery energy storage systems (BESS), high-voltage direct current (HVDC) systems, wind turbines (WTs), and solar photovoltaic (PV) units. Table 4 summarizes this cross-technology comparison, highlighting the relative advantages, limitations, and practical implementation challenges of each technology. This refined framework and accompanying review provide a unified reference for researchers and system operators to better understand, classify, and deploy VI strategies in future low-inertia grids. Overall, this work contributes to closing critical research gaps and lays the foundation for the coordinated development of virtual inertia control (VIC) methods that ensure stable and resilient power systems in the era of high renewable penetration. Modern power grids are increasingly challenged by the lack of inertia caused by the high penetration of renewable energy sources (RES). This low inertia leads to reduced frequency stability and greater vulnerability to disturbances. To address this issue, various virtual inertia (VI) provision strategies have been proposed to emulate inertial behaviour using power electronic converters and advanced control techniques. However, the existing literature reveals two major research gaps. First, there is no unified understanding of VI classification frameworks, as many studies have used diverse categorizations and often treated the Virtual Synchronous Machine (VSM) and Virtual Synchronous Generator (VSG) as equivalent concepts, leading to conceptual ambiguity between grid-forming (GFM) and grid-following (GFL) approaches. Second, most previous research has examined one or a few VI control technologies in isolation, without providing a comprehensive cross-technology comparison that evaluates their relative suitability and dynamic performance under varying conditions. This review addresses these gaps by proposing a new classification framework, which distinctly differentiates between the VSM, VSG, and Synchronverter concepts, while also emphasizing both inertia provision and inertia emulation aspects. This refined framework enhances the understanding of how various VI-based converters contribute to grid stability through either the active production or the imitation of inertial response. Furthermore, the paper provides a structured and comparative review of VI strategies across multiple renewable energy applications—including electrolyzers, electric vehicles (EVs), battery energy storage systems (BESS), high-voltage direct current (HVDC) systems, wind turbines (WTs), and solar photovoltaic (PV) systems—based on their control architectures, frequency response capabilities, and integration potential in future low-inertia grids. The outcomes of this study aim to support researchers and system operators in selecting and developing appropriate virtual inertia control (VIC) methods for maintaining frequency stability in evolving power systems.