Wide Bangap power semiconductor components are used in an increasing number of applications (automotive, PV, more electric aircraft...). However, using these highly performant devices necessitates a very careful implementation in power modules, regarding both electrical and thermal criteria. Indeed, their small size induces very high loss densities (some hundred watts per cm²). In addition, the very high switching speed of these components requires good management of the parasitic elements within the modules: the inductances must be low to reduce voltage overshoots during current transients and the capacitances must be adapted to limit the generation of electro-magnetic disturbances.
In this context, a high power density technology is currently being developed in our laboratory. It is based on the 3D integration of air-cooled switching cells. This implementation allows an excellent compromise between thermal and parasitic elements: the thermal resistance between junction and ambient can be lower than 1 K/W, and stray inductance in the range of 1 nH. This positions this technology among the best ones in comparison with the state of the art.
At this stage, converters based on low voltage switching cells (48 V) have been modeled, manufactured and tested. The new challenge is to bring this technology the technology to higher voltage (1 kV), and to propose and validate a multiphysics design methodology addressing simultaneously electromagnetic, thermal, voltage withstand and reliability issues.
This thesis will focus on the electro-magnetic modeling of power modules with the objective of proposing design models to manufacture converters with reduced overvoltages on the switching devices, and low EMC disturbances. Collaborations with other national laboratories are planned.
Proposed organization of work:
1. Bibliographic study
The research work will be continuously be carried out together with an in- depth bibliographical study on power modules adapted to fast components and on the methods allowing to model and characterize them.
2. Electromagnetic modeling of switching cells
Starting with a simple switching cell, a methodology for modeling overvoltages will be proposed. It will be based on the use of an electromagnetic modeling software allowing to estimate the values of the parasitic inductances and capacitances, and of a circuit simulator aiming at obtaining the waveforms during the switching.
This methodology will then be extended to multicell power module architectures including electromagnetic couplings between cells.
An important work of detailed experimental characterization will be carried out in parallel in order to validate the obtained models.
3. Modeling of conducted electromagnetic disturbances
The heatsinks being submitted to strong voltage variations (dV/dt) during switching, it is necessary to manage the common mode current generation in order to limit the conducted EMC disturbances. This can be done by using conductive plates as shields or by adding inductive elements within the power module.
Technological solutions will be proposed to limit the EMC disturbances, they will then be modeled and validated experimentally.
4. Design and characterization of switching cells and power modules
After the previous preliminary tasks, full devices based on SiC MOSFETs will be designed by the PhD student in order to realize a functional demonstrator of a static converter, which requirements will be decided during the project. It will be done in collaboration with other students working on this project.
This demonstrator will be characterized and compared to the state of the art.
5. Writing of scientific articles and thesis
Funding category: Contrat doctoral
PHD title: Génie Electrique
PHD Country: FranceOffer Requirements Specific Requirements
- Education: Engineering school or M2 in the field of electrical engineering
- Technical skills: Power electronics, electrical measurements, simulations, electronic CAD
- Soft Skills: strong interest for modeling approach, simulation and experimental validations. Autonomy but at the same time good facilities for team work.Contact Information