A Study on Feasible Region for Islanded Operation Mode in Power Systems with Distributed Generators in Emergency

Abstract - As an expected effectiveness in introducing micro-grid, there are possibilities that the microgrid can improve the electrical power supply reliability. Specifically, micro-grid with islanded operation mode can continuously supply power to loads when a fault, such as large-scale power outage, occurs at the utility grid. When the range of the small scale network which can operate independently is planned in advance, it is easier for DGs (Distributed Generators) to design desirable autonomous operation in islanded state during a grid failure in the upstream network. Inversely, under the assumption that the range of the islanded system changes depending on the fault cases, the control logic should have any robustness. Hence, in this paper, to improve the power supply reliability in small-scale distribution systems, we studied the relationship between inverter control and stability of the islanded mode. Supposing that the inverter control is based on droop characteristics, its parameters have to be adjusted considering the equivalent impedance between the inverter and the center of inertia of the remained part of the system in order to realize the stable islanded operation in various fault cases.