For its ability to improve the system reliability by bringing the potential of the distributed generators (DGs) into full play under fault conditions

island partition has become an important operation mode. Based on the characteristics of the DGs and islanded operation of the distribution network

the combined power supply expression of different reliability types for DGs is established. And according to the load level and controllability

the priority to recovering the first-level and second-level load is given based on meeting the various security constraints. A mathematical model based on island partition of distribution network is developed. As all solutions are found using analytical expressions of mathematical optimization

the solution optimization is realized to the full. The effectiveness and practicability of the model proposed is proved by a number of test results. This work is supported by National Natural Science Foundation of China (No. 51107011

No. 51167001) and the Scientific Research Foundation of Guangxi University (No. XBZ120037).