This work introduces a grid-connected island microgrid in China, Luxi Microgrid, with a flexible system structure and a hierarchical control framework. To solve the low reliability issue of original electricity supply on island caused by insufficient generation and transmission capacity, a novel renewable energy system with battery energy storage was proposed in this paper. Dual-microgrid structure is adopted for the new island microgrid to provide flexible and reliable electricity services, based on 24 switching processes among 8 system configurations. The test results demonstrate that the proposed system provides seamless switching and uninterrupted power supply through the use of high voltage fast transfer switch and matched mode switching strategy. Moreover, hierarchical control framework is developed for the implement of flexible and reliable control concept, which consists of three layers: the monitoring and dispatch layer, the coordination control layer and the local control layer. The operational data are also brought forth and analyzed to provide significant and useful experiences for designing and developing similar microgrids in future.