Grid-connected VSI Protection from Grid-side Faults based on Voltage

With the increasing use of renewable energy sources, the need for reliable and efficient grid-side inverter fault detection and protection is becoming more important. Because the magnitude of fault current in semiconductor devices is so small, typical safety systems using overcurrent relays are inadequate. This study addresses a voltage-based protection method for a three-phase inverter that includes grid-side fault detection and an automatic islanding system after a grid fault. Until the grid fault is cleared and the inverter returns to grid-connected mode, the inverter takes care of its own local load and operates in island mode.