Reliability-driven DC-link optimization for fault-tolerant 3L T-type eVTOL propulsion inverters

Abstract This article proposes a mission-profile-based sizing methodology for DC-link capacitors in eVTOL propulsion inverters. While DC-link capacitors contribute significantly to converter volume, traditional design relies on conservative worst-case operating points, leading to significant oversizing. To address this, an electro-thermal modelling approach is developed to evaluate capacitor lifetime based on core temperature fluctuations throughout a dynamic flight profile. The methodology accounts for thermal properties, modulation strategies, and the effects of fault-tolerant operation. Although the method is applicable to various inverter topologies and capacitor technologies, the three-level T-type (3L-TT) fault-tolerant converter benefits most, as demonstrated by an exemplary design achieving a 37.5% reduction in DC-link volume compared to conventional methods while for a specified life-time goal.