The following are some known concerns arising from interconnection of different scale PV systems to the utility grid. (See E-Reserves via the Library Resources tab.) Grid-connection challenges

If for any reason the grid loses power, this bimodal system uses a separate dedicated distribution panel to support the critical loads (such as computers, lighting, water pumping, etc.) (Dunlop, 2010).Д«ook chapter: Mertens, K and Hanser K.F., Photovoltaics: Fundamentals, Technology and Practice, Chapter 7, Section 7.2 Grid Connected Systems, pp. Here, the energy storage provides backup for critical loads, while the excess power is fed to the grid, like in the interactive mode. If the produced power is greater than the on-site power demand, the excess power is fed to the grid.ДЇinally, the bimodal connection (Figure 11.8c) combines both stand-alone and interactive options. If the on-site power demand is higher than the amount supplied from the PV, the system can draw power from the grid.

In this case, power can flow in both directions. The interactive mode does not use any energy storage, and the inverter serves as the interface between the PV and the utility grid (Figure 11.8b). If the battery storage is depleted, the system becomes stressed. The stand-alone mode does not involve grid connection, but rather uses the battery storage to collect the power from PV and convert it to AC for specific applications (Figure 11.8a). They include stand-alone, interactive, and bimodal inverters. Interconnection typesД«y the type of interconnections, there are several inverter types employed at different PV systems. The estimates of the system maximum voltage and currents are key factors for choosing the inverters, determining wiring, conductor size, and required overcurrent protection. In summary, the cables within each string should be able to withstand currents of 6 A, but the cables on the inverter side should be ready for 18 A. I max(output) = I max(source) Г— n par = 6 A Г— 3 = 18 A If we have three parallel strings of modules (like shown in Figure 11.7), each with source maximum current of 6 A, then

Connectivity for power utility grids