This project aims to study a key feature of the Smart Grid as power systems of tomorrow. This feature is the transversal study between the Transmission system simulation and those of the Distribution System. Some prefer to call it as T&D co-simulation. More specifically, this project is about T&D Optimal Power Flow optimization with a consideration of the battery storage technology in the distribution level. The problem is modeled as a Mixed Integer Non Linear program that is resolved in a distributed fashion each minute to insure a safe and optimal operation of lare and dense power systems.