  With the increasing impact of low inertia due to the high penetration of
distributed generation, virtual synchronous generator (VSG) technology has been
proposed to improve the stability of the inverter-interfaced distributed
generator by providing "virtual inertia". This paper presents a recent review
of virtual inertia control covering significance, features, design principles,
and state-of-art inertia strategies from both physical and mathematical
perspectives to facilitate the wide application of the VSG. The definition and
source of virtual inertia are given to help researchers to establish the
concept of "virtual inertia". Then, this paper covers influencing mechanism
studies of virtual inertia to reveal its functions. Also, a design framework of
the virtual inertia is established by considering both the characteristics of
the control system and the limitation of energy storage systems and renewable
energy resources. Finally, several novel adaptive inertia control strategies
are reviewed, and some aspects of potential future research are recommended.
