The increasing trend for integrating renewable energy sources into the grid to achieve a cleaner energy system is one of the main reasons for the development of sustainable microgrid (MG) technologies. As typical power-electronized power systems

MGs make extensive use of power electronics converters

which are highly controllable and flexible but lead to a profound impact on the dynamic performance of the whole system. Compared with traditional large-capacity power systems

MGs are less resistant to perturbations

and various dynamic variables are coupled with each other on multiple timescales

resulting in a more complex system in-stability mechanism. To meet the technical and economic challenges

such as active and reactive power-sharing

volt-age

and frequency deviations

and imbalances between power supply and demand

the concept of hierarchical control has been introduced into MGs

allowing systems to control and manage the high capacity of renewable energy sources and loads. However

as the capacity and scale of the MG system increase

along with a multi-timescale control loop design

the multi-timescale interactions in the system may become more significant

posing a serious threat to its safe and stable operation. To investigate the multi-timescale behaviors and instability mechanisms under dynamic inter-actions for AC MGs

existing coordinated control strategies are discussed

and the dynamic stability of the system is defined and classified in this paper. Then

the modeling and assessment methods for the stability analysis of multi-timescale systems are also summarized. Finally

an outlook and discussion of future research directions for AC MGs are also presented.