• Energy Research

Electric Vehicles (EVs) are becoming one of the main answers to the decarbonization of the transport sector and Renewable Energy Sources (RES) to the decarbonization of the electricity production sector. Nevertheless, their impact on the electric grids cannot be neglected. New paradigms for the management of the grids where they are connected, which are typically distribution grids in Medium Voltage (MV) and Low Voltage (LV), are necessary. A reform of dispatching rules, including the management of distribution grids and the resources there connected, is in progress in Europe. In this paper, a new paradigm linked to the design of reform is proposed and then tested, in reference to a real distribution grid, operated by the main Italian Distribution System Operator (DSO), e-distribuzione. First, in reference to suitable future scenarios of spread of RES-based power plants and EVs charging stations (EVCS), using Power Flow (PF) models, a check of the operation of the distribution grid, in reference to the usual rules of management, is made. Second, a new dispatching model, involving DSO and the resources connected to its grids, is tested, using an Optimal Power Flow (OPF) algorithm. Results show that the new paradigm of dispatching can effectively be useful for preventing some operation problems of the distribution grids.

Abstract In the last years, electric vehicles (EVs) are getting significant consideration as an environmental-sustainable and cost-effective alternative over conventional vehicles with internal combustion engines (ICEs), for the mitigation of the dependence from fossil fuels and for reduction of Green-House Gasses (GHGs) emission. However, many challenges are still ongoing to their large scale implementation. Among them, the negative impact on the electrical grid operation in case of an uncoordinated contemporary charging of a huge number of EVs. In the recent literature different solutions are proposed for handling the peak demand of EVs and the related problems. One answer is offered by the implementation of EV charging strategies, through aggregation agents, for containing the impact on the grid, guaranteeing the quality of the service. The implementation of a real charging strategy is strictly related to a deployment of smart-grid technologies, such as smart meters, Information and Communication Technologies (ICTs) and energy storage systems (ESSs). In particular ESSs are playing a fundamental role in the general smart grid paradigm, and can become fundamental for the integration in the new power systems of EV fast charging stations of the last generation: in this case the storage can have peak shaving and power quality functions and also to make the charge time shorter. In the present paper, an overview on the different types of EVs charging stations, in reference to the present international European standards, and on the storage technologies for the integration of EV charging stations in smart grid is reported. Then a real implementation of EVs fast charging station equipped with an ESS is deeply described. The system is a prototype, designed, implemented and now available at ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development) labs. A wide experimental activity has been performed on the prototype system in order to test its functionalities in the integration in a smart grid available at the same ENEA lab, including a smart metering system. The integration has been possible thanks to the use of a customized communication protocol, developed by the researchers and here described. The results of the experimental tests show that the system has a good performance in the implementation of peak shaving functions, in respect of the main distribution grid, making the prototype like a network nearly zero-impact system.

The present paper includes the results of a wide experimental survey concerning current and power consumptions of some single-phase loads supplied in Low Voltage (LV). In particular home/office equipment has been monitored during its starting phase. For the purpose a custom monitoring system has been implemented and used. The results of the monitoring survey has permitted the characterization of spectrum variability of the single load, that can be useful both for knowing its harmonic behavior, for clustering the equipment, and finally for getting information that can be used for their control in a smart n-grid. The main novelty of the work is to propose a new way to consider transient analysis by suitably coupling the sensing step, usually envisaged in the signal acquisition stage, with a classification step driven to discriminate the transient typology.

Standby energy is actually one of the largest electrical end use with the largest potential energy savings in the residential sector. In the paper, a model of the residential customer's demand using a bottom-up approach, implemented in a load simulator, has been used in order to evaluate the impact of standby end users on Italian average households' daily load shape. Finally, some more diffuse standby power demand management options have been simulated thus allowing predict possible impacts directly on daily load shape.

The present paper deals with storage resources optimization strategies to be adopted in the context of the European Electricity Markets by the Italian Transmission System Operator (TSO), in order to exploit, as much as possible, existing and future storage resources. The state-of-the-art of grid-scale storage technologies deployment in Italy is provided. Then, a critical review of a large set of existing optimization algorithms proposed in literature is presented, with a main focus on pumping hydro optimization approaches, since this is the predominant storage technology available in Italy today. Having not found an approach that perfectly fits with the Italian Transmission System Operator, considering the structure of the electricity markets and the operational planning processes, a new approach is proposed to cope with these requirements.

In a smart micro-grid (MG) each generator or load has to take part in the network management, joining in reactive power supply/voltage control, active power supply/frequency control, fault ride-through capability, and power quality control. This paper includes a new concept for building integration in MGs with zero grid-impact so improving the MG efficiency. These aims are shown to be achievable with an intelligent system, based on a dc/ac converter connected to the building point of coupling with the main grid. This system can provide active and reactive power services also including a dc link where storage, generation, and loads can be installed. The system employed for validation is a prototype available at ENEA Laboratories (Italian National Agency for New Technologies). A complete and versatile model in MATLAB/SIMULINK is also presented. The simulations results and the experimental test validation are included. The trial confirms the model goodness and the system usefulness in MG applications

Eco-driving is one of the most important strategies for significantly reducing the energy consumption of railways with low investments. It consists of designing a way of driving a train to fulfil a target running time, consuming the minimum amount of energy. Most eco-driving energy savings come from the substitution of some braking periods with coasting periods. Nowadays, modern trains can use regenerative braking to recover the kinetic energy during deceleration phases. Therefore, if the receptivity of the railway system to regenerate energy is high, a question arises: is it worth designing eco-driving speed profiles? This paper assesses the energy benefits that eco-driving can provide in different scenarios to answer this question. Eco-driving is obtained by means of a multi-objective particle swarm optimization algorithm, combined with a detailed train simulator, to obtain realistic results. Eco-driving speed profiles are compared with a standard driving that performs the same running time. Real data from Spanish high-speed lines have been used to analyze the results in two case studies. Stretches fed by 1 × 25 kV and 2 × 25 kV AC power supply systems have been considered, as they present high receptivity to regenerate energy. Furthermore, the variations of the two most important factors that affect the regenerative energy usage have been studied: train motors efficiency ratio and catenary resistance. Results indicate that the greater the catenary resistance, the more advantageous eco-driving is. Similarly, the lower the motor efficiency, the greater the energy savings provided by efficient driving. Despite the differences observed in energy savings, the main conclusion is that eco-driving always provides significant energy savings, even in the case of the most receptive power supply network. Therefore, this paper has demonstrated that efforts in improving regenerated energy usage must not neglect the role of eco-driving in railway efficiency.