Flavio Ciccarelli

Improvement of Energy Efficiency in Light Railway Vehicles Based on Power Management Control of Wayside Lithium-Ion Capacitor Storage

The paper suggests an energy management control strategy of wayside Li-ion capacitor (LiC) based energy storage for light railway vehicles (LRV). The installation of wayside supercapacitor (SC) storage devices, as widely recognized, allows the recovery of the braking energy for increasing the system efficiency as well as a better pantograph voltage profile. A new type of SC, LiC, interfaced with dc-interleaved converter has been presented. This technology has an energy density comparable to batteries and power density much higher than the batteries. The authors propose a control strategy based on the maximum kinetic energy recovery throughout braking operations of the running vehicles. The stored energy comes back to the vehicles during the accelerations. The strategy stays on the knowledge of the state of charge of LiC device and the actual vehicle speeds. In particular, the control algorithm evaluates, in real time, the actual value of LiC voltage and current references on the basis of the vehicles inertial forces and acceleration estimations, taking into account the power losses of the system. Experimental tests made on electromechanical simulator, equipped with a 136-V, 30.5-F LiC module, fully confirm the validity of the suggested control. Finally, experimental characterization of LiC module has been achieved.

Line-Voltage Control Based on Wayside Energy Storage Systems for Tramway Networks

This paper presents a control strategy for the power flow management of a wayside energy storage system based on a supercapacitor technology installed in a tramway network. The control is based on the management in real time of voltage levels at catenary point connections in order to optimize the energy flow among the running tramcars and substations with the goals of improving the energy saving and reducing the voltage drops in the supply network. The suggested control algorithm was experimentally validated using a laboratory-scale model to verify the effectiveness of the strategy. A lithium-ion capacitor module with 72 series-connected laminated cells of the JSR Micro ULTIMO type was used. Thus, an emulation of a real tramway network in the city of Naples (ANM) was implemented to evaluate the potential impact in terms of costs/benefits of the next installation on the ANM network.

Modeling and Parameter Identification of Lithium-Ion Capacitor Modules

Lithium-ion capacitors (LiCs) are novel storage devices with a high power density and high energy density compared to conventional supercapacitors (SCs). This paper proposes a method to validate the previously developed characterization and modeling methods, which are the same as those used for a conventional SC with double-layer-activated carbon technology. This paper presents two relevant contributions. First, a full frequency range model and the experimental parameter identification of two kinds of LiC cells are presented. In order to extend the LiC cell parameter identification to a module composed of several series-connected cells, an aggregate model of the LiC module was investigated and validated. The results of experiments and numerical simulations demonstrate the value and effectiveness of the proposed model when the cells operate at room temperature.

An ultra-fast charging architecture based on modular multilevel converters integrated with energy storage buffers

The paper presents power converter architectures for ultra-fast charging of road electric vehicles with the integration of distributed energy storage systems, which work as energy buffer between the grid and the electric vehicle in recharge. The study is introduced by an overview of the main issues related to the charging infrastructures in terms of electric vehicles charging times and their impact on the main grid. The paper continues with an analysis of ultra-fast charging infrastructures with particular focus on applications based on three-phase low voltage AC grid. Then, the proper design of modular multilevel converter architectures is presented taking into account its integration with energy storage modules of different technology, in order to reduce power requirements from the grid during the ultra-fast recharging phase. Different control strategies was proposed and simulated in terms of power flux control, during the charging and the discharging phase of the energy buffers, and voltage balancing among the different energy storage modules on the grid side.

Optimal Control of Stationary Lithium-Ion Capacitor-Based Storage Device for Light Electrical Transportation Network

Storage systems are recognized as a viable mean for improving the performances of electrified transportation systems. The recent literature highlighted some significant solutions to design problems thanks to procedures-based upon optimization theory. More specifically, an analytical solution can be deduced based on the formulation of an isoperimetric problem. This formulation exhibits the intrinsic ability to determine the optimal storage size, once the train power absorption has been fixed. Unfortunately, the analytical expression is not very advantageous to the control because it includes terms that require both real-time traction load estimation and its prediction over the whole traction cycle. The originality of this paper lies in the suitable simplification of the control structure, avoiding both traction load estimation and the heavy computations linked to predictive analysis. The storage device control law is reduced to an appropriate constant voltage over the whole traction cycle. The traction load prediction is performed offline, and the robustness of the consequent control law is tested against random variations in significant traction parameters. Some comparisons are made using other control strategies proposed in the technical literature. Finally, numerical and experimental results confirm the validity of the affected assumptions.

Overview of Lithium-ion Capacitor Applications Based on Experimental Performances

Abstract The use of storage systems is increasing in many applications. At the same time, new technologies for realizing storage devices are being proposed every year. Lithium-ion capacitor (LiC) cells can be included in these innovative technologies. In this study, extensive experimental research was carried out to determine the performance characteristics of LiC cells for practical applications. This study assessed the preliminary results of characterization tests to evaluate the performance of LiC cells over wide temperature and frequency ranges. In order to characterize the cells at different frequencies, galvano-electrochemical impedance spectroscopy (EIS) was performed at different temperatures and polarization voltages. Tests were performed on both laminated and prismatic cells in order to compare their behaviors. Finally, the experimental results were analyzed in order to assess the potential applications of this storage technology.