  This paper focuses on power distribution networks featuring distributed
energy resources (DERs), and develops controllers that drive the DER output
powers to solutions of time-varying AC optimal power flow (OPF) problems. The
design of the controllers is grounded on primal-dual-type methods for
regularized Lagrangian functions, as well as linear approximations of the AC
power-flow equations. Convergence and OPF-solution-tracking capabilities are
established while acknowledging: i) communication-packet losses, and ii)
partial updates of control signals. The latter case is particularly relevant
since it enables an asynchronous operation of the controllers where the DER
setpoints are updated at a fast time scale based on local voltage measurements,
and information on the network state is utilized if and when available, based
on communication constraints. As an application, the paper considers
distribution systems with a high penetration level of photovoltaic systems, and
demonstrates that the proposed framework provides fast voltage-regulation
capabilities, while enabling the near real-time pursuit of AC OPF solutions.
