Photovoltaic charging station for Plug-In Hybrid Electric Vehicles in a smart grid environment

It has been estimated that, there will be one million Plug-In Hybrid Electric Vehicles (PHEVs) by the end of this decade. There is a growing risk that, this proliferation in the number of PHEVs will trigger extreme surges in demand while charging them during rush hours. To mitigate this impact, a unique charging station architecture is proposed in which the rate of charging of the PHEVs is controlled in such a way that the impact of charging during peak load period is not felt on the grid. The power needed to charge the plug in hybrids comes from grid-connected photovoltaic generation or the utility or both. The three way interaction between the PV, PHEVs and the grid ensures optimal usage of available power, charging time and grid stability. The system designed to achieve the desired objective consists of a photovoltaic system, DC/DC boost converter, DC/AC bi-directional converter and DC/DC buck converter. The output of DC/DC boost converter and input of DC/AC converter share a common DC bus. A unique control strategy based on DC bus voltage sensing is proposed for the above system for efficient transfer of energy. By using the proposed control strategy, the operations of charging station can be categorized into four modes: grid-connected rectification, PV charging and grid-connected rectification, PV charging and grid-connected inversion.