The scope of this thesis includes control and management of the Modular Multilevel Converter (MMC)-based Multi-Terminal Direct Current (MTDC).
PhD Swann GASNIER “Decision support framework for offshore wind farm electrical networks: Robust design and assessment under uncertainties’’
Large offshore wind farms will be important players within the future energy landscape. What is the expected benefit for a project is an essential issue from Investor side, considering both technical and economic aspects. Levelized Cost Of Energy - LCOE - is a standard economic indicator which allows to assess the economic viability of a project.
Common understanding today is that the challenges to develop the SuperGrid are huge at many levels (e.g.: political, societal, economical, financial, scientific, technical…). It is also commonly accepted that the SuperGrid will require novel technologies (breakers, cables, converters…) and operating principles (e.g.: transition from a more passive essentially AC-based power system to a more active AC/DC-based one). This thesis deals with the development of a key actor for SuperGrid technology, that is, AC/DC converters.
To connect the different points of the network, the transmission and distribution of electric power used cables. Since few years, cables and especially their insulation part are evolving, going from paper insulation to a synthetic insulation. Nowadays, the insulation part of HVDC cables is in crosslinked polyethylene or XLPE.
High Voltage Direct Current (HVDC) converters are composed of hundreds of semiconductor switches connected in series to sustain the rated voltage of the converter (several hundred of kilovolts). Because of the large number of switches, it is highly probable that at least one of them will fail during the lifetime of the converter. Such failure should not cause the entire converter to shut down, despite the series connexion of the switches. As a consequence, each switch should be designed so that upon failure, it becomes a short circuit and keeps carrying the current (“fail-to-short” behaviour).
PhD Albert PEREIRA “Design methodology of a medium frequency transformer for high voltage and high power DC-DC converters”
The transmission and distribution of electric power is normally made by ac networks (50 Hz or 60 Hz), where one of the key elements of this infrastructure is the power transformer; used for more than a century, its design is very well understood, with a level of operating efficiency normally greater than 99%.
PhD Houssem Eddine NECHMI “Research of gas/ gas mixture without sulfur hexafluoride for High Voltage Insulation applications”
SULPHUR hexafluoride, SF6, is the most common compressed gas used in high voltage power equipment since the 1950s and in HV transmissions and substations applications (GIS, GCB, GIL …), SF6 holds a prominent place because of its dielectric and chemical performance (high dielectric strength, non-toxicity, low condensation temperature, thermal stability, non-flammability, chemical inactivity with the other constituent materials of the apparatus, availability and moderate cost). It is one of the best insulators gas known today.