  We combine the power flow model with the proportionally fair optimization
criterion to study the control of congestion within a distribution electric
grid network. The form of the mathematical optimization problem is a convex
second order cone that can be solved by modern non-linear interior point
methods and constitutes the core of a dynamic simulation of electric vehicles
(EV) joining and leaving the charging network. The preferences of EV drivers,
represented by simple algorithmic strategies, are conveyed to the optimizing
component by real-time adjustments to user-specific weighting parameters that
are then directly incorporated into the objective function. The algorithmic
strategies utilize a small number of parameters that characterize the user's
budgets, expectations on the availability of vehicles and the charging process.
We investigate the collective behaviour emerging from individual strategies and
evaluate their performance by means of computer simulation.
