The scientific activity is oriented towards the study of the methodologies, modelling and techniques for the analysis, control and prototyping of power converters, electrical machines and drives.
Theoretical studies are conducted in the fields of e-mobility, aircraft applications and electrical railway traction and experimentally validated power electronics systems and electrical drives to investigate the problems of energy efficiency and energy saving. These studies have focused on the integration of energy storage devices and renewable energy sources into power converters, along with their energy management. In particular, double layer capacitors called 'supercapacitors' have been investigated.
The main themes of TRLab research can be classified as follows:
1. Ultrafast EV-Charging Station;
2. Energy saving in light railway and road vehicles;
3. Anti-skidding phenomena in high-speed trains.
Ultrafast EV-charging station
A modular multilevel converter (MMC) architecture has been proposed for the ultra-fast charging of road electric vehicles with the integration of distributed energy storage systems, which work as an energy buffer between the grid and the electric vehicle during recharge. These studies are introduced by an overview of the main issues related to the charging infrastructures in terms of electric vehicle charging times and their impact on the main grid. The activity is continuing with an analysis of ultra-fast charging infrastructures, with particular focus on applications based on a three-phase medium voltage AC grid. Then, an appropriate design for a modular multilevel converter architecture is presented, taking into account its integration with energy storage modules of different technologies, in order to reduce the power requirements from the grid during the ultra-fast recharging phase. Different control strategies are proposed and simulated in terms of power flux control, during the charging and discharging phases of the energy buffers, along with voltage balancing among the different energy storage modules on the grid side. Currently, a first prototype of an MMC integrated with a lithium ion capacitor (LiC) has been realized. The results of these studies are utilized in an Italian patent application with the start-up company ‘PnPLab’ .
Energy saving in light railway and road vehicles
These studies are conducted in the framework of the research project SFERE with Ansaldro Breda, the company’s team leader, in the field of railway traction. The objective of the project is the realization of an on-board storage system for energy recovery during the braking operations of light railway vehicles. The installation of a supercapacitor stack based on LiC technology is carried out on the vehicle SIRIO along the tram-way of Naples. The main contribution is the implementation of real-time controls for on-board energy management for maximum energy recovery. A stand-alone configuration and integrated solution for a power converter with the traction inverter is suggested. The energy management control algorithm is based on speed measurement and acceleration estimation. The aim of the control is to recover, in a supercapacitor storage device, the maximum energy regenerated during a train’s electrical braking and to limit the contact line peak current. The energy management control is integrated with the motor drive control, because the discharge and charge of the SC are connected to the motoring and braking operations of the train. Experimental tests are conducted on an electromechanical simulator. These studies are continuing in order to verify the possibility of replacing the traditional traction inverter with a modular multilevel converter (MMC) integrated with energy storage devices. The main problems focus on the control of MMC during start-up, when the DC-voltage fluctuations are quite large.
Future Directions
Long-term goal is to carry out interdisciplinary research that can provide researchers and engineers coming from industry insights through mathematical modelling and analysis. I plan to explore a broad array of topics that arise from the transformation of the current electric power networks into a smart grid. There are interesting open directions in the area of the integration between the service infrastructures for e-mobility in urban areas:
Static and dynamic charging for EVs
Inductive power transfer (IPT) was an engineering curiosity less than 30 years ago, but, since that time, it has grown to be an important technology in a variety of applications. Since then, applications for the technology have diversified and, at the same time, have become more technically challenging, especially for the static and dynamic charging of electric vehicles (EVs), where IPT offers possibilities that no other technology can match. Here, systems that are ten times more powerful, more tolerant of misalignment, safer and more efficient may be achievable, and if they are, IPT can transform our society. The challenges are significant, but the technology is promising. One of these is the power supply requirement in terms of the high-frequency operation of power converters (up to 100 kHz). New power transistor families such as generation 6 insulated gate bipolar transistors (IGBTs) and silicon carbide (SiC), which have negligible recovered charge, allow H-bridges to switch VAR loads without difficulty at frequencies up to more than 50 kHz. These make fixed frequency switching the clear choice for most IPT power supply applications. Next year, an interesting start-up project, based on IPT technology, will involve inductive static recharging at an e-bike station on the campus of the University of Naples.
New power supply system for 1.5 kV catenaries
Nowadays, the increase in regional traffic, especially on the main axes of railway networks, and the heavy freight train traffic require more power to the catenaries. Unfortunately, because of its relatively low voltage level, a 1.5 kV DC system is limited by the high current level absorbed by trains, which causes important line voltage drops. In order to increase the capability of the 1.5 kV DC system, a new topology based on a feeder transmitting a part of the total power with a voltage that is double the catenary voltage has been proposed to SNF by Prof. Ladoux at the Laplace Laboratory of Toulouse. In this framework, next year, a PhD thesis on the design of a DC/DC system will be planned with co-advisors at the Laplace Laboratory and the University of Naples ‘Federico II’. The goal is the development and testing of gate drives for a modular line voltage booster based on 3.3-kV SiC technology.