Planning studies for active distribution grids in presence of EVs charging stations: simulation on a real test network

In the next future, a large spread of Electrical Vehicles (EVs) is foreseen, in accordance with the European policies and regulation dealing with environmental sustainability. It will lead to an important number of charging stations connections, whose number will be a function of the demand required by the EVs (traffic conditions, EV fleet and features, etc.), but they depend also on grid capacity, considering that they typically represent very variable loads for the grid. A “fit and forget” approach could involve the violation of grid operation limits and so the need of grid reinforcements (new MV and LV lines construction, primary and secondary substations expansion or new construction), thus causing relevant investments on the distribution grids. An intelligent management approach for EV charging stations could ensure the respect of the operation limits of the grids in the actual asset. The same approach should take into account the presence of DG and coordinate the RES energy production with the new EV charging stations consumption, solving technical problems such as the reverse power flow. In this way it should be possible to defer or avoid network reinforcements and development. The paper shows some results of a wide planning study performed on a real active distribution grid, including EVs charging stations connected to MV grid (public stations) and LV grid (home stations) in different EVs spread scenarios, according to European addresses, Italian policies, Enel guidelines and making a study of the territory where the distribution grid is located. Simulations have been carried out on the MV and LV grids connected to a HV/MV transformer. The complete analysis has been based on Power Flow (PF) and Optimal Power Flow (OPF) calculations performed using a MatLab tool. PF analysis gave the possibility to know the hosting capacity of the distribution grid for EV charging stations, pointing out if grid reinforcements are required. OPF analysis allowed evaluating the impact of a smart management approach, taking full advantage of the actual hosting capacity of the grid, suitably dispatching the EV charging stations. Many objective functions have been tested with the MatLab tool. Some of the results are reported in the paper for showing the benefits of the smart management approach in terms of grid reinforcements avoided.