Control coordination of power converters on the distribution grid to enhance overal system stability
With the increasing number of generation and consumption units connected through power electronic converters, the electrical grid is evolving toward a more dynamic and decentralized structure. This transformation strengthens both the need and the potential for these converters to actively contribute to system flexibility and stability—particularly in compensating for renewable energy fluctuations and maintaining the balance between supply and demand.
Optimized coordination of their control functions offers significant potential to improve grid resilience, by intelligently leveraging their capabilities in voltage regulation, frequency support, and reactive power control. However, to integrate these contributions effectively at scale, it is essential to develop holistic modeling approaches that capture multi-scale interactions—both in time and space.
The modeling work in this thesis aims to represent the relationship between the active/reactive power flexibility of power electronic converters and the stability margin they provide to the grid, as well as to model the aggregation of their actions for system-wide contribution. Building on this foundation, coordinated control architectures and algorithms between the distribution and transmission networks will be investigated, developed, and validated.
Study of the Metastability of Silicon Heterojunction Solar Cells and Stabilization Strategies
Silicon-based photovoltaic cells, particularly silicon heterojunction (SHJ) cells using hydrogenated amorphous silicon (a-Si:H), achieve efficiencies exceeding 25%. However, these architectures exhibit intrinsic metastability, such as Staebler-Wronski degradation, which can lead to efficiency losses during storage between fabrication and module assembly. In the context of globalized supply chains, these instabilities represent an economic and technical risk that is not yet well quantified. This thesis aims to address the following questions: what is the quantitative impact of instability on the efficiency of high-efficiency cells during prolonged storage? What are the physical mechanisms responsible for this degradation? What technological strategies can reduce or eliminate this instability? What are the industrial implications for module logistics? To achieve this, a rigorous experimental protocol will be implemented to monitor the electrical performance of cells over several months under varying storage conditions (atmosphere, temperature, humidity). Test structures and advanced characterizations (FTIR, Raman, Silvaco TCAD) will be used to understand the underlying physical phenomena. Process optimization, introduction of new materials, and improved packaging will be explored to stabilize the cells. Practical recommendations for the industry, regarding maximum storage durations and optimal storage conditions, will also be established. The goal is to develop technological and logistical solutions to minimize efficiency losses in SHJ cells, optimize supply chains, and reduce associated economic risks.
Development and characterization of a low-silver metallization for photovoltaic cells with high-efficiency passivated contacts
In order to decarbonize energy production and meet climate plan objectives, the production of photovoltaic (PV) modules must increase significantly. To sustain these production levels, the silver content in latest-generation cells must be drastically reduced. Some alternatives incorporate less expensive metals (nickel, aluminum, copper) into screen-printing pastes. These approaches require evaluation in terms of contact formation, electron transport, and reliability. In a TOPCon cell architecture, the electrode must be brought into direct contact with the active layers of the cell via thermal annealing. This step enhances device performance (through a hydrogenation phenomenon) while simultaneously generating potential degradation related to the introduction of metallic species. This is especially critical when using new metals (Ni, Cu, etc.) with higher diffusivities than silver. The objectives of this thesis are manifold: to evaluate the performance of these low-silver alternative pastes once integrated into TOPCon cells; to characterize the impact of the introduction of these metallic species on the lifetime of photogenerated carriers in silicon; and to assess the long-term stability of these metallizations while verifying the absence of cell degradation phenomena under prolonged illumination. If necessary, an alternative metallization technique more suitable for these pastes will be developed. During the PhD, the successful candidate will be required to fabricate, metallize via screen printing, and characterize devices within a cleanroom environment.
Self-healing of radiation-induced defects in silicon solar cells for space
Over the last decades, the development of alternative space photovoltaic (PV) solutions to the III-V premium standard has shifted the focus to silicon solar cells. Indeed, leveraging on existing maturity of terrestrial PV silicon devices and processes offers significant potential for innovation and cost reduction. Many satellites nowadays evolve in Low Earth Orbit, a proton and electron rich environment. Such irradiations induce electrically active defects in the material which affect the PV performances. Interestingly, some of the irradiation-induced defects can be healed upon external factors such as temperature and/or photons flux.
The main goals of this PhD thesis will be to i) understand the bulk & interface electron/proton irradiation-induced degradation mechanisms driving the evolution of the optoelectronic properties of silicon passivated contacts solar cells ii) develop a comprehensive understanding of the self-healing effects in irradiated modern silicon solar cells through experimental studies and modeling iii) identify design / fabrication process routes to control & boost the self-healing capability.
To reach these goals, this PhD work will go through defined steps: bibliography review, solar cells fabrication, material/device ageing under proton & electron irradiations, advanced characterizations and modeling. This PhD work will be conducted at CEA/Liten, on the INES campus (Le Bourget du Lac, FR) with frequent interactions with CNES (Toulouse, FR) facilities.
Intelligent control and optimization of DC microgrids using digital twins in real-time simulation
This thesis addresses the challenge of decarbonizing industrial and territorial systems by proposing a transition to direct current (DC) microgrids controlled by a Digital Twin. Faced with the saturation of alternating current (AC) grids due to the growth of photovoltaics, energy storage, and electric mobility, DC allows for a reduction in conversion losses (5 to 15%), improved flexibility, and a simplification of the electrical architecture.
The project is based on the development of a high-fidelity Digital Twin synchronized in real-time simulation. More than just a monitoring tool, it acts as a proactive decision-making system integrating advanced optimization algorithms, such as artificial intelligence and predictive control. It anticipates voltage instabilities, which are particularly critical in low-inertia DC grids, and continuously optimizes power flows to maximize self-consumption while preserving battery life.
Experimental validation relies on a Hardware-in-the-Loop approach within the CEA-Liten/G2Elab ecosystem, integrating physical converters. This methodology guarantees robustness, security, and resilience before any real-world deployment.
The expected outcomes are scientific (stability and real-time modeling), operational (provision of technical guides and decision-making tools), and strategic (strengthening French technological sovereignty in Smart Grids and accelerating the 2050 carbon neutrality trajectory advocated by ADEME).
Exploring the Strategic Benefits of 0V Storage for Na-ion Batteries
Recently deployed on a commercial scale, the Na-ion battery technology demonstrates excellent behaviour during medium or long-term storage at zero voltage. This characteristic offers numerous safety advantages during the transport, assembly and storage of cells and modules, as well as during emergency shutdowns in the event of external issues. But are there no consequences for battery performance?
This research project aims to study and better understand the electrochemical mechanisms at play when the potential difference across the terminals is maintained at 0 V.
Initially, advanced dynamic characterisation techniques will be used to analyse and compare the electrochemical, thermal and mechanical properties of battery materials. The results will enrich calendar and cycling ageing models at the cell scale, thereby improving their accuracy and reliability. Subsequently, tests will be conducted on mini-battery modules assembled in various electrical architectures to study cell behaviour during cycling and ageing, particularly in response to the application of negative voltage. Specific battery management system (BMS) solutions could then be proposed to address these issues.
The scientific approach will involve implementing advanced characterisation and instrumentation techniques, conducting ageing and safety tests to identify mechanisms, and developing ageing models. This approach will draw on the expertise and testing facilities of CEA-Liten at the Bourget du Lac site in Savoie.
Development of Zinc Sodium-ion batteries for stationary storage of renewable energy
In the global context of massive renewable energy deployment, production and storage are becoming increasingly intertwined. Battery electrochemical energy storage systems (BESS) are currently experiencing strong market growth. These systems differ radically from electric mobility solutions due to their specific characteristics (cost, safety, durability). Faced with the limitations of Li-ion batteries (fire risks, the criticality of lithium and cobalt, production costs), aqueous zinc/sodium-ion technology presents a disruptive alternative. Based on abundant, non-toxic, and inherently safe materials, it offers unique potential for long-term storage with a low environmental impact. The zinc battery sector faces scientific challenges that limit reversibility and cycle life, notably the formation of zinc dendrites and cathode instability. This doctoral thesis project proposes to overcome these obstacles through a research and development strategy for innovative electrodes based on the reversible transformation of zinc into zinc phosphate in an aqueous sodium phosphate medium. This choice of electrolyte allows the use of sodium-ion positive electrodes as well as AGM (absorptive glass mat) separators, developed notably for lead-acid batteries.
The thesis work will focus on experimental electrochemical studies combined with multiphysics modeling of the system at the cell scale, taking into account the thermodynamics and kinetics of the included reactions. This approach will allow for the rapid exploration of a vast design space to identify the conditions enabling scaling up and transfer to industry, meeting the imperatives of energy sovereignty and the circular economy.