We suggest a grid-connected photovoltaic (PV) system in which PV arrays and batteries are connected directly in DC side. In this system, batteries are discharged or charged under control by power-conditioner which converts the mixed output of PV arrays and batteries without a DC-DC converter for converting a battery voltage. Despite a shift of a power point of PV arrays from maximum power point, it is possible to increase power generation of PV arrays because conversion loss of the DC-DC converter can be removed. As a result of numerical simulations, it is found that the power generation ratio of this system to MPPT system reaches to 97.4%.
