Grid-Interactive Electric Vehicle DC-Link Photovoltaic Charging System

The transportation sector currently accounts for 70% of petroleum consumption and more than a third of green house gas emissions in the US. Studies have shown that  major reductions in GHG emissions can be accomplished by transitioning to battery powered automobiles. However, the large battery systems required could be problematic due to high cost in combination with limited specific energy, safety issues, as well as limited cycle and calendar life. 

A DC-to-DC converter takes a direct current from one voltage level and stores it to later converted to a direct current at a different voltage level. Efficient operation of large battery systems like those of battery powered automobiles require relatively high DC voltage. Because a single battery cell has a  fairly low voltage, the need for higher voltage is commonly resolved by placing a large number of battery cells in series. However, this method is often problematic, in that a battery is only as good as its weakest cell and there are too many inconsistencies between individual cells for the system to be reliable. Therefore there is a need for each cell in the string to include protection devices to prevent catastrophic failures due to overcharge, excessive discharge, or excess temperature.