Islanding Operation of Electrical Systems in Buildings Control Methods for Voltage and Frequency Regulation and Re-synchronisation

A control system was developed, which allows on-site generators within a building to operate in islanding mode, in the event of loss of grid supply. The on-site generation included a photovoltaic array and a back-up induction generator. Regulation include avoidance of sudden voltage and frequency changes at the transition to islanding mode, maintaining voltage and frequency within limits during islanding, and phase matching when the grid supply is re-established. Possible modes of operation during islanding were photovoltaic array alone, generator alone, or both sources operating in parallel. Control methods were considered for each of these, and the resulting voltage and frequency regulation was anal sized. The results show that voltage and frequency could be kept within limits, except during the transitions to and from islanding. At these times, the transients were minimised