Off-grid system means that the electric energy generated by photovoltaic power generation system is stored in storage battery and converted into alternating current by inverter for direct use by electrical equipment, or directly used by DC electrical equipment without inverter, and is not connected to the power grid.

Grid-connection means that photovoltaic power generation is converted into alternating current by inverter, connected to the power grid through boosting or direct low-voltage side, and the power is dispatched and used by the power grid.