Microgrid Islanding Detection with a Hybrid Method

As the fast integration of Distributed Generators is developing rapidly, it has become mandatory for the Microgrids to be more stable and controllable to feed the loads connected, uninterruptedly. The general condition of any Microgrid is in synchronism with the main grid in a normal way. This is also as per the Department Of Energy of United States of America . The IEEE-1547 standards also say that the Microgrid must have the robust islanding detection method, incorporated in the interfaced inverter, to detect the fault within the time duration specified. For this purpose an efficient islanding detection method, which is a hybrid technique utilizing both passive and active islanding types is proposed in this paper. The passive one is, Rate of Change Of Frequency (ROCOF) and the active type is reactive current injection at inverter output terminals. The islanding detection is achieved with the cumulative sum of rate of change of frequency(CSROCOF). With this method, the low active power mismatch at point of common coupling is also compensated and the islanding detection is achieved in the specified time as prescribed by the standards. With all these controls embedded, the false detection and tripping of the Microgrid, islanding from maingrid is avoided. The non detection zone area is also substantially reduced. The proposed methodology has been tested in Matlab / Simulink environment and the results prove the efficiency of the method.