Abstract:

Microgrids are attracting increasing interest since they are allowed to work under islanding mode by being disconnected from large-scale commercial distribution networks when large disasters occur. However, disconnected microgrids do not contain appropriate protection systems, which in most cases are installed only at distribution substations. Moreover, the fault currents are significantly limited due to the high penetration of inverter-based distributed generators (IBDGs). Therefore, a protection system or scheme targeted at islanding microgrids is required. In this paper, we develop a transient analysis for islanding ungrounded microgrids, in which multiple IBGDs are deployed under different control strategies, during different types of faults. Furthermore, we propose a fault detection and location method based on two-terminal measurements instead of the singleterminal measurements often utilized in conventional protection schemes such as overcurrent protection. The proposed method does not rely on heavy information exchange. We monitor zerosequence components, negative-sequence components, and phase currents for locating different types of faults in islanding microgrids. It is verified in our simulation study that the proposed method works well in islanding microgrids with lower fault current levels.