  This paper studies the problem of output agreement in networks of nonlinear
dynamical systems under time-varying disturbances. Necessary and sufficient
conditions for output agreement are derived for the class of incrementally
passive systems. Following this, it is shown that the optimal distribution
problem in dynamic inventory systems with time-varying supply and demand can be
cast as a special version of the output agreement problem. We show in
particular that the time-varying optimal distribution problem can be solved by
applying an internal model controller to the dual variables of a certain convex
network optimization problem.
