Thesis (PhD) - Combined Experimental and Digital Twin Approach for Assessing the Degradation of Si-IGBT and SiC-MOSFET Modules in Railway Traction Converters W/M

Créée en 2014, SuperGrid Institute est une société privée indépendante, acteur de la transition énergétique en France et dans toute l'Europe, regroupant plus de 150 collaborateurs et plus de 20 nationalités différentes. Spécialiste des systèmes électriques innovants à courant continu en haute et moyenne tension (HVDC et MVDC). SuperGrid Institute participe également au développement de nouvelles technologies pour l'intégration des énergies renouvelables dans les réseaux électriques du futur.

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Key words: Power electronics, Digital twins, Lifetime models, Accelerated tests, CHM, Statistics

General context

During a converter's service life, operating costs significantly contribute to its total cost. To optimize maintenance expenses, the current trend is shifting from corrective maintenance toward condition-based maintenance (initiated by degradation detection), and ideally toward predictive maintenance (initiated by failure prediction).

Subject of the thesis

The R&D team at SuperGrid Institute (Villeurbanne), in collaboration with Alstom and with the support from Politecnico di Torino (Italy), is offering an exciting research work part of the POWERDIAG project, funded by the French National Research Agency (ANR).

The development of advanced conditions and health monitoring functions for power electronics converters used in railway traction relies on validated and robust lifetime models for each degradation mechanism, robust algorithms for the prediction of Remaining Useful Life (RUL) and trained Digital Twins.

The validation of these approaches is challenging because they must be implemented in the early design phase while their benefits are expected in the long term (a railway converter is designed for 30 years typically) with no possibility to run test without acceleration factors.

As a consequence, dedicated methodologies and test benches must be developed in order to generate the necessary datasets to support the validation activities.

Supergrid Institute has developed a multi-stress test bench combining accelerated load cycling stress with hard switching under high voltage, high current conditions to be as close as possible to the real application conditions. Phenomena at different time scale are reproduced on this test bench (from semi-conductor switching ( #10 µs) to reproduction of a railway use profile in the minute range). This test bench is extensively instrumented (Vce, Vce sat, I load, I switch, Vge, Tcase, Tjunction, …). A new test bench with higher current and voltage capabilities will be designed during the project to perform Power Cycling Test (PCT) and also Short-circuit stress, for Si IGBT but also SiC MOSFET.

Objectives / Missions

In this context, the PhD candidate will be responsible to diagnose the state of health and prognose the remaining lifetime of SiC Mosfet and Si IGBT in the context of Railway Traction Converters by combining experimental data with a digital twin. A specific focus will be made on a multi-stress test plan to maximize the learnings in the context of railway power modules. Also, a digital twin of the power module will be developed and used both to optimize the test plan and to simulate long term degradation.

This thesis aims to provide answers to the following key questions:

1. In the context of railway traction applications, what are the specific electrical, thermal, and mechanical stresses experienced by power modules, and what degradation mechanisms are expected to lead to their failure?

2. How to design an appropriate accelerated multi-stress test plan that considers the relevant combinations and magnitudes of stressors, while incorporating the statistical variability of the influencing factors?

3. How to choose, measure and extract the relevant data-set from the accelerated ageing tests to train the Digital Twin (data volume vs precision) ?

4. How can the test plan be optimized for a given technology, considering the industrial need to minimize the number, duration, and cost of tests while maintaining their relevance?

5. How can a digital twin of the power module be designed, parameterised, and validated so that it can interpolate and extrapolate test conditions, and simulate long-term degradation caused by a typical railway mission profile?

Degree in Electrical Engineering, specialising in Power Electronics. Knowledge of semiconductor physics would be appreciated.

• Electrical engineering and power electronics, in particular :

  • Signal processing, metrology, sensors and instrumentation

  • Physics of ageing mechanisms

• An aptitude for experimental work

  • Operation of test benches

  • Development of measurement methods (digital and analogue electronics)

• Fluency in French and English.

• Knowledge in system modeling, component reliability, and statistical processing of experimental data

Soft Skills

• Strong analytical and summarising skills;

• Teamwork;

• Autonomy;

• Thoroughness;

• Organisational skills;

• Curiosity and creativity;

PhD Supervisor: Francesco IANNUZZO
Enrollment Institution: Politecnico di Torino
Industrial Supervision: SuperGrid Institute, in collaboration with Alstom
PhD Candidate Location: Mainly at SuperGrid Institute, Villeurbanne (France), with possible mobility to Politecnico di Torino (Italy)
Duration and Start Date: 3 years, starting from November 2026

Join a dynamic team within a leading applied research institute, working closely with the railway industry

What we can offer you :

• You'll be joining an institute working on the energy transition, a buoyant and stimulating field of activity,

• A young and dynamic working environment,

• Mixed, international teams (over 20 nationalities),

• Company restaurant (contribution to meal costs),

• Possibility of teleworking 1 day/week,

• Sports activities within the company (yoga, football, running, etc.),

• Work Counsil allowances, Health insurance, Life and disability insurance

• Sustainable Mobility Bonus ("accord de mobilité durable")

• Profit Sharing Bonus ("accord de participation et d'intéressement)

• 12 RTT days per year

Other information

When you join SuperGrid Institute, you'll be part of a dynamic working environment.

At SuperGrid Institute, we respect and value the diversity of our employees, their backgrounds and experiences, with the aim of providing equal opportunities for all.

Diversity is at the heart of our operations and we are committed to banning all discrimination from our human resources management. SuperGrid Institute makes all its positions accessible to people with disabilities and is committed, as part of its action plan for professional equality, to paying particular attention to applications from women in order to achieve a balanced overall distribution of the workforce.