Thermal Measurement of Asymmetric Losses in a Submodule of an Isolated Modular Multilevel DC-DC Converter

Abstract

In this work, asymmetric loss distribution between the high-side and low-side devices of an Isolated Modular Multilevel DC-DC Converter (IM2DC) submodule (SM) is identified and experimentally quantified, revealing that low-side devices can dissipate up to twice the losses of their high-side counterparts. This imbalance indicates unequal semiconductor utilization, with direct implications for thermal design and long-term reliability in modular DC-DC architectures. To investigate this phenomenon, a steady-state calorimetric method based on thermal imaging is applied directly to a half-bridge SM while the full converter operates under various voltage levels. The approach provides accurate, non-intrusive loss measurements and is validated through analytical estimations with an absolute error below 0.07 W. These findings lay the groundwork for future optimization of IM2DC converter design and control.

José Andrés Aguilar Croston (SuperGrid Institute and INSA Lyon) ;
Narges Moeini (School of Electrical and Computer Eng., Georgia Institute of Technology) ;
Jean-Yves Gauthier (INSA Lyon, CNRS, Universite Claude Bernard Lyon 1, Ecole Centrale de Lyon, Ampère, UMR5005) ;
Cyril Buttay (CNRS, INSA Lyon, Universite Claude Bernard Lyon 1, Ecole Centrale de Lyon, Ampère, UMR5005) ;
Besar Asllani (SuperGrid Institute) ;
Piotr Dworakowski (SuperGrid Institute) ;
Maryam Saeedifard (School of Electrical and Computer Eng., Georgia Institute of Technology)

Presented at IEEE Applied Power Electronics Conference and Exposition (APEC) 2026

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