Electrical power systems and methods using bidirectional power converters to provide, among other functions, uninterruptible power supplies for loads such as cell towers. The power-packet-switching power converter can be connected, for example, to a photovoltaic array, batteries, and a critical load such as a cell tower. An AC generator can also be connected in order to power the cell tower and/or to charge the batteries as needed. Green energy utilization is maximized, power conversion efficiency is increased, and system costs are decreased, by having only a single power conversion stage for all conversions.