The student Olatz Lizaso Eguileta obtained an EXCELLENT grade, with an International Doctorate mention and an Industrial Doctorate mention.

The student Olatz Lizaso Eguileta obtained an EXCELLENT grade, with an International Doctorate mention and an Industrial Doctorate mention.

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• Thesis title: Module-Level Modelling Approach for Li-Ion Batteries: a Cloud-based Digital Twin Simulation Platform

Court:

• Presidency: Maitane Berecibar Uribe (Vrije Universiteit Brussel)
• Vocal: Urtzi Lazcano De Anta (CEGASA ENERGIA S.L.U)
• Vocal: Franz Pichler (Virtual Vehicle Research GmbH)
• Vocal: Luis Trilla Romero (IREC)
• Secretary: Erik Garayalde Perez (Mondragon Unibertsitatea)

Abstract:

The adoption of large-scale Lithium-ion Batteries (LIBs) has been steadily growing. These installations involve interconnecting multiple batteries to create powerful systems capable of storing megawatt-hours (MWh) of energy. LIBs have emerged as a promising solution for electrical energy storage, thanks to declining prices and improved manufacturing efficiency. This accessibility has driven increased demand for LIBs in applications like electric vehicles and stationary systems.

In the case of LIBs, particularly in module configurations, individual heterogeneities and imbalances among cells pose significant challenges. These disparities can compromise energy efficiency and overall lifespan of the battery module. While extensive studies have focused on individual cells, there remains a gap in understanding and addressing module-level effects and complexities.

This thesis proposes an innovative methodology for developing module-level battery models that encompass thermal and electrical components, as well as a State of Charge (SoC) estimator. These models are derived from widely used cell-level models using equivalent circuits. A detailed thermal model captures cell interactions within the battery system, while an electrical model simulates individual cell behavior. An approach to implement these models in a cloud-based simulation platform enables performance estimations and issue identification.

The proposed methodology has been validated through laboratory testing using a prototype. Tests demonstrate the accurate operation of the thermal and electrical models, as well as the SoC estimator at the cell level. These models are then adapted to the module level, accounting for electrical and geometric characteristics. Additional tests on the module prototype verify the successful extrapolation of cell-level models to the module level. Two case studies have been conducted to evaluate the capability of the developed models to detect heterogeneities and imbalances. These case studies involved the introduction of anomalies in the laboratory prototype, such as voltage imbalances between module cells and thermal imbalances using a thermal blanket. In both cases, the models showed the ability to detect irregularities in the module.

In general, the methodology proposed in this thesis allows to have a holistic model of a LIB at module level, which represents the electrical and thermal behaviour of each of the cells that compose the module, thus contributes to a better understanding allowing an adequate monitoring of the system.