Abstract: Taking the Dingjie microgrid renovation project as the background, this paper constructs a power supply assurance microgrid system with the core objective of ensuring continuous power supply for critical loads in the county, so as to prevent the risk of a total outage. To ensure smooth project implementation, a digital-analog hybrid simulation and testing platform based on RTDS is established according to the primary system architecture of Dingjie County. Grid simulation modeling and closed-loop testing of control devices are carried out. System simulation tests are completed under typical scenarios, including grid-connected operation, planned and unplanned transition from grid-connected operation to islanded operation, islanded operation, transition from islanded operation to grid-connected operation, and black start after a total outage.