Input Admittance Shaping-based Active Islanding Detection Technique for Multi-inverter Microgrids

Abstract

Deploying grid ancillary services through distributed energy resources (DERs) challenges islanding detection techniques (IDTs). Power regulations, for instance, may mitigate power mismatches in islanded microgrids, increasing the risk of undetected islands. Additionally, when the grid is connected, false islanding detection during low-voltage events can disrupt low-voltage ride-through (LVRT) operations. Existing IDTs that comply with these services and requirements often suffer from power quality degradation and limited scalability in multi-inverter systems. To address these gaps, this study proposes an active IDT using the DER's input admittance shaping within a narrow negative-sequence frequency band. The shaped admittance results in a negligible negative-sequence disturbance (NSD) injection during grid-connected operation while ensuring rapid and synchronized NSD jump after island formation in multi-inverter systems. Thus, islanding is detected when the rate of change of negative-sequence voltage at the DER terminal exceeds a preset threshold within a specified timeframe. Importantly, the proposed IDT does not affect the positive sequence component, avoiding conflict with ancillary services in grid-connected operations. Numerous simulations are conducted in PSCAD-EMTDC in accordance with the IEEE Std. 1547.1-2020 test procedure. The results demonstrate precise and rapid islanding detection in single- and multi-inverter scenarios, including zero/small power mismatches with DER's power regulations. In addition, the proposed IDT does not exhibit false tripping during low-voltage events, complying with LVRT requirements.