Master in Electrical Energy and Systems Engineering

Design and analysis of electric generators for off-shore wind farms

Wind farms are one of the renewable sources from which the largest developments are expected in the next future. The trend is towards increasing the number of wind farms, but also the size of each single turbine is going to grow considerably. Currently, the rated power for each turbine unit is typically smaller than 1 MW, but in the near future power ratings in the order of tens of MW’s are expected to be achieved. This is posing huge technological challenges not only with respect to turbines but also regarding the electric generators coupled to them. In fact, reliability reasons lead and often force designers to remove gear boxes (which are breakable components with complicated maintenance). As a results, the electric generator, in the direct-drive arrangement, has to revolve at such low speeds as 10-15 rpm and, thereby, it has to develop huge torques that are typically in the order of billions of N´m’s.

Electromagnetic sizing and design of micro-wind generators

Wind generation is a “clean energy” source which is expected to experience the highest growth in the near future among the various renewables. If suitably exploited, wind energy can, in fact, remarkably (although discontinuously) contribute to meet the global electric power demand. Wind energy can be exploited at different levels and in different ways, ranging from off-shore wind farms to micro-wind generators to be installed in domestic and urban environments. All the applications, however, call for special electric generators to be coupled to wind turbines. Such generators need to be carefully sized and designed to meet application requirements, which often include demanding constraints in terms of size, noise, vibration and wide-speed-range operation.

The Dept. of Engineering and Architecture - DIA at the University of Trieste has taken part in various research projects intended to develop new wind generator prototypes, mainly in cooperation with InterWind and with Nidec-ASI.

"Dependable-oriented" design of All Electric Ships Integrated Power Systems

In the ships endowed with electric propulsion (namely AESs - All Electric Ships), the power system is essential and vital, because all the onboard loads are powered by it. However, in case of ships in which a black-out is extremely harmful (due to economic and environmental reasons, in case of offshore Oil&Gas applications, or due to the failure of the mission, in the case of naval vessels) it assumes a major role. Therefore, for such vessels the main design goals for the Integrated Power System (IPS) are: ensure the required power quality, defined as quality of the electric power supplied to the ship's loads; ensure a high continuity of service, intended as the possibility to keep the ship in operation as much as possible. Because of the vital role that the IPS has in AESs, the above-mentioned objectives are closely related to all the other possible objectives of the project, such as performance, efficiency, safety, maintainability, and environment protection.

Fault currents in shipboard medium voltage direct current distribution systems

The adoption of innovative distribution systems on ships (such as the Direct Current distribution) is hampered by the current lack of standards for the calculation of fault currents in DC distribution systems with nominal voltage greater than 1kV. Furthermore, unlike what happens in AC distribution systems, the extreme variability (in terms of generation and conversion systems) in the possible DC current production methods onboard ships makes it extremely difficult to define simplified formulas for the fault currents calculation.

For these reasons, a research activity it is in progress, aimed at determining the short circuit currents on board ship in DC systems with rated voltage above 1kV (defined MVDC distribution - Medium Voltage Direct Current distribution).

High Voltage Shore Connections

In the very last years, the High Voltage Shore Connection (HVSC) has represented one of the best technical solutions to supply ships at berth without operating shipboard prime movers, thus reducing air pollution in city ports. Taking into account the potentiality of this technology, on one hand it is possible to notice the interest of several city ports throughout the world, on the other also the shipyards have started to design shipboard power systems capable of supplying ships at berth. Considering a single ship, the requested power may be about 10 MW in order to keep certain services running during berthing.

The voltage control of MVDC shipboard power systems

Nowadays, the Medium Voltage Direct Current (MVDC) distribution represents an interesting possibility for improving the future shipboard power systems. The concept is based on the widespread use of power electronics equipment, in order to interface generating systems and loads to the MVDC bus (rated voltage higher than 1 kV). This technology is able to provide several advantages, among others easy integration of storage systems and reduction of the power system’s weight/volume. On the other hand, it is important to highlight the need of a proper voltage control system, even more in presence of tightly controlled load converters. Indeed, the contemporaneous presence of high bandwidth controlled converters and filtering stages (RLC filters) may determine dangerous voltage oscillations and instability after a load connection.

Naval Smart Grid

Title: Naval Smart Grid (NaSG) - Integrated Power System for All Electric Naval Vessels with control and reliability characteristics - research project PNRM (National Research Military)
Period: March 2013 - December 2015 (in progress)
Client: NAVARM (Directorate of General Naval Armament) - Italian Navy
Leader: University of Trieste – Lab. EPGC.
Other partners: Sapienza - University of Rome
Polytechnic of Milan.

Advanced Control Method for Robust Stability of MVDC Systems

Title: Advanced Control Method for Robust Stability of MVDC Systems - research project ONR (Office of Naval Research - Global Office, London UK)
Period: October 2011 - July 2013
Client: ONR (US Navy Office of Naval Research) - Global Office, London UK
Leader: RWTH Aachen University - Institute for Automation of Complex Power Systems
Other partners: University of Trieste – Lab. EPGC

MVDC Large Ship

Title: MVDC Large Ship – Medium Voltage DC integrated power system for Large electrically propelled Ships - research project POR-FESR
Period: October 2010 - January 2014
Client: Regione Autonoma Friuli Venezia Giulia
Leader: Fincantieri SpA
Other partners: University of Trieste (Scientific lead) – Lab. EPGC
Polytechnic of Milan
University of Udine
Blu Electra SRL
Area Science Park
RINAVE consortium

Research