Assessing solar PV inverters´ anti-islanding protection

This paper provides an overview of the islanding potential of solar photovoltaic (PV) inverters. Solar PV inverters are typically known to have very effective protection mechanisms, but concerns have been raised as to whether or not they could maintain an island if load and generation were closely matched and/or if there were additional sources of distributed generation on a circuit. Also provided are the test results of multiple solar PV inverters operating in parallel during a variety of islanding scenarios. Additional tests included evaluating German inverters to investigate whether or not advanced features (such as volt/VAR controls and low-voltage ride-through) and load matching can compromise the solar PV inverters´ anti-islanding protection. The testing was performed in Southern California Edison´s Distributed Energy Resources Laboratory in Westminster, California. The results detailed here provide information that can be used to develop national standards for advanced features on solar PV inverters. Residential U.S. inverters have a nominal voltage of 240 V line to line, and German inverters are 230 V line to neutral. The frequency of the German inverters was adjusted to 60 Hz to reflect American standard practices.