Conception et réalisation de convertisseur à base de composants GaN

The rise of electric mobility requires solutions that increase the energy efficiency and mileage of vehicles. There is potential for improvement in power electronics, which is important for converting electrical energy into an ever-increasing number of on-board functions (recharging batteries, powering motors, lighting). For this goal, the new gallium nitride (GaN) semiconductor devices are very promising, because they allow a high energy conversion efficiency and a high operating frequency, resulting in a saving of consumption and useful space to increase the energy stored on board.

However, their implementation requires a perfect understanding of the device and system parameters which can no longer be neglected in this case, such as their dynamic resistance and parasitic inductances, even small, of the switching meshes and of the gate circuit. To make full advantage use of the outstanding electrical properties of GaN components, it is necessary to characterize them finely in order to develop reliable models in simulation. Design methods and tools will then be developed to accelerate the implementation of these components into power converters, which will eventually realize the consumption and autonomy gains expected by GaN technology and contribute to the development of clean mobility.

This thesis will be carried out jointly between the University of Lille and the Coventry University (UK). Based on previous research discoveries on novel GaN device characterisation and modelling method, this PhD project will expand the collaboration to a wider area for EV-based power electronics converter. As the Coventry region has historically been an important center of the automobile industry in the United Kingdom, the development of skills around electric mobility is a strategic challenge carried by the Lille and Coventry universities. Thus, the "e-Mobility" is one of the main research axes for the laboratories of the two universities which include power electronics teams.

Goal :

The proposed research subject aims to design static converters operating at high frequency and using new GaN components for the conversion of on-board electrical energy in electric or hybrid vehicles. In order to make the best use of the excellent electrical properties of GaN transistors, it is necessary to determine their performances in terms of power losses and switching waveforms, which are sensitive to parasitic elements of the circuit. The work carried out during this thesis should include characterization and modeling of the multi-physical parameters impacting the different operating phases of the GaN transistor.

The objective is to develop a reliable model to represent the behavior of the component during the various operating phases and which will be used in the design by simulation of converters operating at high frequency. The model chosen must be generic and adaptable enough to cover the various GaN transistor technologies on the market. Design rules can then be defined and integrated into a tool making it possible to quickly validate the implementation of GaN transistors in a static converter. The proposed design approach will make the best use of the electrical performance of GaN devices and make HF converters adapted to the specific constraints of integration in vehicles, with high efficiency and high power density. An EMC analysis of the disturbances generated by the converter will also be carried out in order to include the Electromagnetic Compatibility (EMC) constraints in the design process.

By facilitating the robust implementation of GaN components in on-board converters, the results of the thesis should encourage the use of this technology in electric and hybrid vehicles. The electrical performance of these new components, judiciously exploited, will have to improve the energy efficiency of these systems, helping to reduce the energy consumption of vehicles by optimizing the on-board weight, size and conversion efficiency. The power density of the power converter achieved by the high-frequency operation of GaN components and by the reduction of the dimensions of the cooling systems allows improving the electric vehicles mileage. This research work is therefore fully in line with the objectives of developing clean mobility.

Funding category: EU funding