Modern power systems wherein renewable resources such as solar and wind power are extensively used need to rely on some means for energy storage to address the intermittency of such resources. This proposal investigates a class of power electronic converters that are able to connect battery energy systems to the grid and provide multi-directional pathways for the flow of energy. Various models will be developed for these converters to facilitate their design, analysis, and computer simulations. A large number of advanced studies will be conducted to assess the performance of these converters in networks with high levels of renewable penetration.