A study of islanding in utility-connected residential photovoltaic systems. I. Models and analytical methods

Models and methods for the analysis of the continued operation of a group of utility-connected photovoltaic systems even after loss of the utility source are presented. The methods involve an examination of steady-state power balance under islanded conditions, an examination of large-signal, limit-cycle behavior, and an examination of the effect of specific control systems on the small-signal stability of islanded conditions. In conjunction with each other these methods allow a determination of whether islanding can occur in a specific system. Although all such systems have a natural propensity to island, it is shown that the controls used in many commercially available units make islanding a rather unlikely phenomenon