Enhanced Islanding Detection for GFM and GFL Inverters Using Negative Sequence Current Injection

An advanced islanding detection method applicable to both grid-following (GFL) and grid-forming (GFM) inverters is newly proposed in this paper. The proposed method overcomes the key limitations of conventional techniques, namely the non-detection zone (NDZ), while offering practicality and cost-effectiveness by eliminating the need for additional communication infrastructure. By injecting a negative sequence current component, the proposed method effectively identifies islanding even in scenarios where the inverter-based resource (IBR) output power matches the load demand, a condition under which conventional techniques typically fail. This solution is robust against various grid and load conditions, ensuring reliable islanding detection for both GFLs and GFMs. The effectiveness of the proposed method has been validated through simulations and experimental tests, demonstrating that islanding can be detected stably with only 2% negative sequence current injection relative to the positive sequence in a 380 V/60 Hz system. The results confirm that the proposed method is highly suitable for enhancing the reliability and safety of inverter-based distributed energy resources.