  Electric vehicle (EV) charging can negatively impact electric distribution
networks by exceeding equipment thermal ratings and causing voltages to drop
below standard ranges. In this paper, we develop a decentralized EV charging
control scheme to achieve "valley-filling" (i.e., flattening demand profile
during overnight charging), meanwhile meeting heterogeneous individual charging
requirements and satisfying distribution network constraints. The formulated
problem is an optimization problem with a non-separable objective function and
strongly coupled inequality constraints. We propose a novel shrunken
primal-dual subgradient (SPDS) algorithm to support the decentralized control
scheme, derive conditions guaranteeing its convergence, and verify its efficacy
and convergence with a representative distribution network model.
