Strategy for Detecting Island Operation Mode of Three-Phase Four-Wire Microgrids

Three-phase, four-wire microgrids enable the supply of both single-phase and three-phase loads. Power electronic converters in these systems facilitate the integration of renewable resources from both DC and AC sources, ensuring high power quality. One of the characteristics of microgrids is their ability to operate either connected to or disconnected from the power grid (island mode). Therefore, they must meet specific requirements to guarantee the power quality and protection of both converters and equipment connected to the microgrid. This article proposes a fast method for detecting the Island operation mode based on the instantaneous trajectory of the grid current vector in the three-dimensional αβ0 reference frame, capable of isolating the system during different single- and three-phase grid interruptions. The proposal is integrated into the control strategy of a three-phase, fourleg inverter, allowing feed nonlinear and unbalanced loads in four-wire applications. Simulation results validate the proposed strategy, demonstrating effectiveness and speed in detecting a fault condition in the power grid, enabling the operation in the island mode of the microgrid.