Implementation and testing of anti-islanding algorithms for IEEE 929-2000 compliance of single phase photovoltaic inverters

Electrical system islanding occurs when the utility grid is removed but local sources continue to operate and provide power to local loads. This can present safety hazards and the possibility of damage to other electric equipment. Anti-islanding functionality is a key requirement for grid-interactive inverters used in PV systems that function as distributed generation sources. The IEEE Std. 929-2000 "Recommended Practice for Utility Interface of Photovoltaic (PV) Systems" (IEEE 929) sets testing requirements for these systems which includes an anti-islanding requirement. UL has adopted this practice in UL-1741. This paper provides a description of Xantrex anti-islanding algorithms and examples of inverter testing. Inverters tested were the Xantrex SW with GTI and ST models. Testing was performed at the Sandia National Laboratories Distributed Energy Technologies Laboratory. Data is provided for single and multiple units with additional data on power quality.