Electricity is a key energy vector in the global shift away from fossil fuels. It is distributed via AC grids connecting power plants to consumers over long distances. Transition policies highlight using medium-scale, medium-voltage distributed generation and storage systems, like France's mandate to cover parking lots with photovoltaic panels. But, these intermediary systems generate DC energy, requiring conversion to AC for grid integration. Medium-voltage direct current (MVDC) grids are an interesting solution for integrating these distributed systems. They offer enhanced energy efficiency, control, and reliability. However, non-standard power converters in DC grids pose issues such as interoperability, high development costs and obsolescence. Our project proposes to improve the modular multilevel converter (MMC) to create standard, modular, robust and scalable power interfaces. The MMC is a converter topology using low-voltage modules in series. This offers genericity in terms of voltage levels. Known for its reliability and robustness, its main drawback is its complex control and data architectures, requiring expensive centralized supervision system. This limits the competitiveness of the MMC for MVDC applications. Our CARROTS project aims to design an open-source generic MMC with masterless cooperative control and a peer-to-peer communication network, suitable for MVDC applications. This 48-month PRCE project involves four research laboratories and a start-up in an interdisciplinary collaboration. We will explore the power, control and data aspects of this challenging proposition while integrating it into an open-source power electronics framework. CARROTS aims to create the first open-source MMC to support international research initiatives, and stimulate innovation in the industry.

The negative capacitance (NC) effect has been presented as a possible solution to the necessary reduction of the switching voltage in field effect transistors and could thus contribute to the future development of low power switching devices. The work that we plan to carry out is mainly positioned in the development of mature static NC structures. This maturity will be reached if we can control and stabilize the physical phenomenon at the origin of this NC. To succeed, it will be necessary to develop heterostructures alternating layers of a few nanometers thick made of ferroelectric (FE) materials on the one hand and paraelectric (PA) materials on the other hand, and to control the quality of the interfaces essential to the stabilization of the NC effect. The choice of materials, the control of epitaxial stresses and electrostatic effects will be crucial to bring the NC phenomenon back to near-ambient temperature ranges. The consortium set up for this project intends to take up this challenge and for that it gathers competences and strengths in the elaboration of heterostructures, the fine characterization at the elementary scale of the materials, of their interfaces, of the structure in ferroelectric domains, the electrical characterization of these structures at the local and macroscopic scale in wide frequency and temperature ranges, clean room technologies for the realization of specific test vehicles. In this context, the objectives of the NEGCAP project are: (i) to fabricate model FE/PA structures in superlattice (for direct measurement of negative capacitance) and multilayer (for indirect measurement of NC), (ii) to determine and model the dielectric response of these structures in a wide frequency range, (iii) to probe the properties at the FE/PA interfaces in order to understand the physical phenomena involved, (iv) to identify the fields of application of these structures and to propose "negative capacitance effect at room temperature" structures.