The new scenario of the Italian electrical system is featured by the exponential growth of Distributed Energy Resources (DER), mostly PV, resulting in a deep change of network planning and operational criteria. Traditional load profiles on distribution network are changing, thus modifying the power plants operation and progressively introducing a new role for the DSO as energy flow manager in an active network, obviously in close coordination with the TSO. So, even for plants connected on LV and MV networks, it is necessary to manage the power of each generator, according to new requirements introduced by the Italian Regulator. Furthermore, the extension of the frequency range in which DER must stay connected to the electrical network, as recently established by Italian Regulator's Acts, has increased the difficulty on managing the high number of connections of DG plants to the distribution network, mainly on LV network, leading to potential unintentional islanding situations. Criteria are being developed in order to prevent this phenomenon, by means of innovative protections using new communication systems such as optical fibre in MV network and PLC systems in LV network. The inverter and its PWM control system are going to have a key role for DER management, and the Interface Protection Relay (IPR), controlled by inverter PWM, is going to drive the disconnection of static generators in case of exceeding frequency or voltage threshold, thus helping the DSO to avoid security problems. In order to cope with the new problems arising in the distribution network, the new Italian technical standards, introduced in 2012, specify the technical requirements that active users must respect to be connected. This paper shows, in the first part, some data related to the increase of DER on Enel Distribuzione's network, with the description of some typical issues that have recently arisen in the operation of the electrical network. The second part describes the developments resulting from the new technical standards for DER connections to the distribution network, the new strategies adopted by Enel Distribuzione and the innovative components and equipments which Enel Distribuzione is already installing to reach a better integration of DER, improving efficiency and reliability of the electrical system.
Renewable Energy Sources based (RES-based) Dispersed Generation (DG) and Electrical Vehicles (EVs) charging systems diffusion is in progress in many Countries around the word. They have huge effects on the distribution grids planning and operation, particularly on MV and LV distribution grids. Many studies on their impact on the power systems are ongoing, proposing different approaches of managing. The present work deals with a real application case of integration of EVs charging stations with ES-based DG. The final task of the integration is to be able to assure the maximum utilization of the distribution grid to which both are connected, without any upgrading action, and in accordance with Distribution System Operators (DSOs) needs. The application of the proposed approach is related to an existent distribution system, owned by edistribuzione, the leading DSO in Italy. Diverse types of EVs supplying stations, with diverse diffusion scenarios, have been assumed for the case study; various Optimal Power Flow (OPF) models, based on diverse objective functions, reflecting DSO necessities, have been applied and tried. The obtained results demonstrate that a centralized management approach by the DSO, could assure the respect of operation limits of the system in the actual asset, delaying or avoiding upgrading engagements and charges.
In Italy a large amount of Dispersed Generation (DG), mainly based on Renewable Energy Source (RES), has been connected in the last years to the distribution grids in Medium Voltage (MV) and Low Voltage (LV) grids of Enel Distribuzione, the main Distribution System Operator (DSO) in Italy, changing the electrical system from passive to active. The diffusion of Electrical Vehicles (EVs) is foreseen for the next future, in accordance with the European policies regarding environmental sustainability, resulting in another important change for the distribution grids: EVs charging stations will be realized as new connections with their very variable load towards the grid, in function of the demand required by the EVs. New planning and operation criteria are thus required for the electrical grid. This paper describes results of a wide planning study performed on a real active distribution grid of Enel Distribuzione, including different types of charging stations (public and home stations) in different EVs spread scenarios. The study shows how a smart management approach for EVs charging stations, recently proposed in many scientific papers, dispatching them taking into account DG and coordinating them with RES energy production, could ensure the respect of the operation limits of the grids in the actual asset, so deferring or avoiding network reinforcements
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