Flexible Grid-Connected/Islanded Switching for Microgrids under Main Grid Faults

With the acceleration of the energy transition and the continuous increase in the penetration of distributed generation, microgrids have become key carriers for integrating distributed energy resources. Consequently, the grid-connected/islanded switching technology is now a core element in ensuring grid resilience and power supply reliability. This paper systematically reviews the research status and development trends of flexible grid-connected/islanded switching technology for microgrids under main grid faults. It comprehensively analyzes the evolution paths, traditional control strategies, and intelligent collaborative methods. Traditional control techniques discussed include improvements in droop control, power compensation, phase pre-synchronization mechanisms, and communication protocol optimization schemes. Intelligent collaborative technologies examined encompass cutting-edge directions such as data-driven control, multi-agent collaborative decision-making, and deep reinforcement learning. Domestic and international case studies reveal the innovative value of PV-Storage-DC-Flexibility (PSDF) systems in practice, summarizing the performance advantages and switching processes of DC microgrid architectures. Research shows that adaptive control strategies can reduce transition processes to millisecond levels, and intelligent collaborative architectures significantly enhance renewable energy accommodation capacity. Finally, challenges such as the accuracy of multi-source data fusion, adaptability to complex fault scenarios, and the stability of hybrid systems are identified as future research priorities. This review provides theoretical references for building high-resilience smart grids.