Bi-directional charging topologies for plug-in hybrid electric vehicles

The automotive industry is going through a major restructuring, and automakers are looking for new generations of hybrid vehicles called plug-in hybrid electric vehicles (PHEVs). In the event that PHEVs become more available and the number of PHEVs on the road increases, certain issues will need to be addressed. One vital issue is the method by which these vehicles will be charged and if today's grid can sustain the increased demand due to more PHEVs. Although these vehicles appear to pose a large liability to the grid, if executed properly, they can actually become an even larger asset. The grid can benefit greatly from having reserves that can store or release energy at the appropriate times. Enabling PHEVs to fulfill this niche will require a bi-directional interface between the grid and each vehicle. This bi-directional charger must have the capability to charge a PHEV's battery pack while producing minimal current harmonics and also have the ability to return energy back to the grid in accordance with regulations. This paper will first review some of the power electronic topologies of bi-directional AC-DC and DC-DC converters that fulfill these requirements and then discuss the best choice for combining two topologies to form a bidirectional charger.