This paper presents a photovoltaic (PV) generator along with a battery energy storage system connected in series with a three-phase grid. The objective of the proposed system is to provide uninterruptable compensation to the series-connected grid and non-linear load during strong sunlight as well as at night or in cloudy conditions. The interface between the grid and the PV is carried out through a voltage source converter (VSC), eliminating both the current and voltage harmonics and compensating the reactive power. The DC voltage control of the DC bus capacitor is employed in order to maintain unity power factor operation of the system, irrespective of changes in solar radiation level or due to change in load. Another control scheme is implemented to charge and discharge the connected battery whenever the sun goes out, to meet the DC bus voltage requirement of the VSC through a bidirectional DC-DC converter.