Admittance control for anti-islanding protection in modular grid-connected inverters

A major requirement for grid-connected power converters imposed by codes and standards is “anti-islanding” protection. When the grid connection is lost or otherwise stops functioning, the photovoltaic power converter is required to shut off to avoid “backfeed” into the local distribution network. This paper describes a “reverse PFC” admittance control that controls the output current of an inverter in response to a detected grid voltage. It is shown that loss of grid will drive the inverter voltage to zero except in a unique special case. The special case can still be detected if the admittance includes a slow phase variation.