This work focuses on the transmission grid level and investigates the control of VSCs interfacing renewable sources in hybrid power systems where PE and SG coexist.
The present thesis investigates the concept of a single-ended fault identification algorithm based on the estimation of the fault parameters.
This thesis identify the major challenges when considering the application of non-selective fault clearing strategy to hybrid grid structures and to propose solutions.
The modelling and analysis are essential in the development of the MFT technology which is attracting lots of research and industrial interest.
The proposed gate driver achieves a better trade-off between losses & conducted emissions compared to the classical series-connected passive resistors for SiC MOSFET gate drivers.
In the framework of the research activities of the High Voltage Substation Equipment program of SuperGrid, it has been proposed to introduce such species by means of an evaporative liquid spray. The interaction between injected droplets and the mixture of hot gases successively flowing into the chamber and vented outside the chamber during the mechanical separation of the electric contacts should allow spray evaporation and transport of the modified gas mixture towards the arc region.
The work of this thesis focuses on the experimental development of a passive and biphasic cooling system to cool down power electronics. Some of those modules are mean voltage power converters developed by Supergrid Institute. Some constraints have been imposed upstream to this project. While some limitations are of the technological nature, other constraints are related mainly to the environmental and biological aspects. The first part of this thesis was to find a suitable cooling system that could be adapted to the project specifications. After some research, we decided to build a loop thermosiphon filled with NOVEC 649.
Energy Transition for a more sustainable world is now the priority in societies. Towards this objective, especially in Europe, the offshore wind energy development has been relatively rapid. For Offshore Wind Power Plants (OWPP) farther from the shore (50 km and beyond) Voltage Source Converter (VSC) based High Voltage DC (HVDC) Transmission has become the prominent solution. Replacement of the offshore VSC station by multiple Diode Rectifier Units (DRUs) led to a cheaper, more compact and robust solution. This thesis focusses on various technological and scientific problems involved in the control system of the Offshore Wind power Plant with Diode Rectifier (DR) based HVDC transmission. These challenges are first reviewed in detail along with the state of the art. Then, based on the system dynamics, a grid forming control scheme is proposed by using the P-V and Q-f droop relationships, with a solution for the synchronization of the wind generators. Moreover, some of the selected control solutions in the literature for this topology are reviewed, compared and assessed by using time domain simulations of a study case. Following this, the different solutions for black start of the offshore AC system are analyzed from the available literature and they are compared using the relevant qualitative criteria. The various faults in the offshore system are then analyzed and the above designed grid forming control scheme is extended with Fault Ride through (FRT) capability, for offshore AC grid faults. Finally, a brief analysis is done on the challenges for the integration of this OWPP topology into a Multi Terminal DC (MTDC) network.
In order to include large-scale renewable sources into the electrical system and to transport high amounts of energy through long distances, the actual AC grid must be upgraded. HVDC transmission grids appear as a promising solution to upgrade the system and answer correctly the future needs and requirements. The development of such grids can be done following two different approaches. For one side, a DC system designed totally from zero following a standardization of HVDC technology, and for the other side, an incremental evolution using the existing HVDC lines. The second approach seems more reasonable due to the reutilization of infrastructure, the inconvenient is that the technology used on each existing line is different. Thus, their interconnection will require DC¬DC converters as interface elements. These structures allow the interconnection of different HVDC schemes and offer more functionalities than only DC voltage adaptation like power flow control and protection.
Thursday 12/12/2019, Thibaut Lefort has obtained the title of Doctor of Materials of Lyon university after a high quality viva. Hence, the thesis jury has strongly encouraged him to candidate for a Ph.D award granted by INSA in the energy category.
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