Historically, distribution systems have largely been passive components of the electric grid that were over designed with little analysis.  In modern power grids, this is no longer the case as it has become increasingly more important and necessary to operate distribution systems at or near their maximum capacity.  Coupled with the challenges faced in reliability, security, environment, sustainability, and market diversity, it is more important than ever to accurately model and control the system.  We propose a hierarchical control architecture where there is a separation between the (slow) time-scale that controls the settings of conventional voltage regulation devices and the (fast) time-scale where voltage regulation through active/reactive power injections is accomplished.  Slow time-scale devices will generally be existing hardware that will be dispatched at appropriate time intervals to reduce the wear on their mechanical parts.  In contrast, fast time-scale devices are considered to be devices that connect to the grid through power electronics and will be used to combat the variability introduced by the distributed energy resources and flatten the voltage profile of the distribution network.