부산대학교 도서관

The fault current in a PV-integrated microgrid (PV-MG) has a relatively low value and an unpredictable phase angle, making current-measurement based fault detection techniques highly unreliable. This paper investigates the ability of conventional distance protection to detect and allocate balanced (LLL-G) faults on MG feeders emanating a PV inverter (PVI). Different PVI grid-support settings are investigated. PSCAD simulations show that conventional distance protection can reliably detect solid LLL-G faults on feeders emanating from PVIs. In the case of non-solid faults, however, conventional distance relays fail due to the unpredictable phase angle between the PVI fault current and the grid fault current infeed. Subsequently, the study proposes a novel high-frequency current injection (HFCI) distance protection scheme capable of accurately detecting faults regardless of fault resistance. PSCAD simulations prove the speed and reliability of the proposed HFCI distance scheme in both grid-connected and islanded modes of operation for both solid and non-solid faults.