This paper proposes a three-stage coordination methodology to optimally manage congestion in day-ahead operation planning for Transmission Systems (TS) and Distribution Systems (DSs). The first stage provides the day-ahead model (DAM) results for the power units in the TS, and Energy Storage Systems (ESSs) and Electric Vehicles (EVs) in the DSs. The second stage applies the DAM results to the modelled TS to reveal any congestion issues. If congestion is depicted the need for congestion management (CM) by the Transmission System Operator (TSO) arises. Thus, the TSO performs an AC Optimal Power Flow (OPF) analysis, under power loss minimization, to provide the redispatch schedule in the TS and quantify the power transactions between TSO and the Distribution System Operators (DSOs). Finally, the DSOs examine if they can deliver these power transactions without congestion in their DSs, by applying AC OPF to minimize power losses. If this is not possible, then a relaxation scheme is applied to these power transactions in order to define the maximum DSO flexibility without congestion in the DS. The proposed methodology is applied to the simulated Greek TS and the results indicate that it can optimally redispatch the available assets with a coordinated interaction between TSO-DSO(s)
