Recently there have been a significant increase in the number of solar rooftop PV systems in the residential households. These renewable based distributed generations provide an alternative clean source of power and allow a significant portion of the load to be supplied locally, reducing the power consumed from the grid. However, in terms of distribution system operation they can cause unexpected adverse effects such as reverse power flow, voltage rise and voltage unbalance. Furthermore, the amount of rooftop solar PVs injected is expected to increase significantly. This makes it essential to reassess the distribution network performance which was originally designed for downstream power flow. This paper presents a three-phase power flow approach based on the current mismatch variant of the Newton Raphson to assess the effect of high penetration of single phase PV units and how energy storage systems can help to mitigate the undesired effect. The paper presents a comprehensive three-phase detailed modeling of the key components in the grid suitable for use with the three-phase power flow algorithm. The strategy to utilize the energy storage devices, to mitigate the issues of rooftop PVs has also been proposed. The results from a 24-hour simulation using data from an actual distribution network in NSW, Australia have validated the proposed models, demonstrated the undesired impacts of the integration of a high penetration of single phase PV units in the distribution grid, and demonstrated the role of storage devices to mitigate the undesired impacts.