A Multi-timescale Stability Analysis Framework for Isolated DC Microgrids

Renewable energy sources have developed rapidly in recent years. In particular, isolated direct current (DC) microgrids have emerged as new grid structures for the comprehensive utilization of renewable energy and have good development prospects in industrial fields. However, the stability analysis of isolated DC microgrids still faces a significant challenge owing to the strong coupling of power converters and abundant transient processes. Thus, a new stability analysis framework for isolated DC microgrids is provided. In detail, the multi-timescale characteristics and stability issues of isolated DC microgrids are first analyzed, and three timescales are defined: the switching period timescale, device control timescale, and system control timescale. Subsequently, the existing stability indices of the microgrids are introduced, and a stability analysis framework for isolated DC microgrids is proposed based on the three defined timescales in this study. Finally, future research directions for the stability of isolated DC microgrids are discussed, and conclusions are drawn. The proposed stability analysis framework provides a reference for solving the stability problems in isolated DC microgrids, such as wide-frequency-band oscillations and the offset of the AC frequency.