Multi-Source Distributed Photovoltaic Anti-Islanding Protection Device Based on Impedance Angle Measurement

With the increasing penetration of distributed generators (DGs) in distribution networks, the issue of unintentional islanding caused by grid outages has become increasingly severe. Impedance-based anti-islanding protection methods, which offer advantages such as small detection blind zones, low false operation rates, and minimal impact on power quality, have attracted significant attention. However, in multi-source distribution networks, variations in DG numbers and mutual interference among injected signals can lead to protection failure. This paper first designs an islanding identification criterion based on impedance angle measurement. Then, a “one-point multi-address” encoding scheme is adopted, where the tripping of any phase simultaneously acts on all receivers in the same district to disconnect photovoltaic (PV) stations. Field experiments demonstrate that the proposed method effectively avoids misoperation and refusal-to-operate issues in existing protections, eliminates potential risks of “islanding operation,” and resolves the long-standing “islanding” hazard in power systems.