Protection of domestic solar photovoltaic based microgrid

A large-scale implementation of distributed generation (DG) for households involves each house generating its energy from photovoltaic (PV) cells. This approach is particularly suitable in rural electrification projects where demand is relatively low and yet grid connection is costly. A meshed microgrid is an attractive solution for energy generation and sharing in domestic electrification projects. Solar PV systems located on different houses can be interconnected together into a meshed microgrid. This interconnection creates an integrated system that can be treated as a single DG. While they remain autonomous, the systems can operate as one microgrid. This approach provides a more reliable and robust grid as the systems can supplement each other. However, protection and control in a meshed power network setup is a challenge. This is because a meshed microgrid has more interconnections and interfaces compared to radial architecture power grid. This is further complicated by effects of DG on power quality, such as transients: voltage sags and swells, under and over-current faults amongst other difficulties. The challenges necessitate robust protection schemes supported by effective control and fault location identification facilities. This paper discusses implementation of islanded or grid-connected microgrids formed by solar systems installed in homes. The paper discusses microgrid protection, adaptive control and fault location identification. In grid-connected mode, power flow in microgrids is bidirectional. This characteristic rules out many of the traditional protection schemes based on current direction. Thus differential current protection scheme is the focus of this paper. In conclusion, this scheme overcomes many protection problems including the low fault current nature of conventional inverters.