The electrification of aircraft marks a pivotal advancement in the pursuit of sustainable aviation, offering substantial environmental and operational benefits. In conventional air- craft, the environmental control system is a major non-propulsive power consumer. In more electric aircraft (MEA), it is electrified using a high-speed motor compressor driven by a voltage source inverter (VSI). The VSI topology selection is a critical, multi-objective challenge as it directly dictates the system’s efficiency, specific power (kW/kg), power density (kW/L), and total harmonic distortion (THD). However, existing topology com- parisons are often inadequate, as they fail to benchmark complete systems within the unique aerospace context and its stringent DO-160G compliance requirements. This thesis addresses this gap by developing a framework to fairly compare VSI topologies at a system level to offer insight for topology selection.
Conventional and interleaved 2-level (2L) and 3-level (3L) VSI topologies are com- pared, including the neutral point clamped (NPC), active NPC (ANPC), and T-type variants. The framework is used for the design and selection of all critical subsystems, including all VSI components, heatsinks, and DO-160G compliant electromagnetic com- patibility (EMC) filters. Interphase inductors are a key performance-defining component in interleaved topologies, so novel analytical expressions for peak and RMS circulation current were derived to inform their systematic design. This framework then evaluates the performance of each topology against the key metrics by sweeping design choices, includ- ing variations in switching frequency, number of parallel devices, and circulation current limits.
The framework was applied to a 20 kW aerospace compressor system, revealing there is no single ’best’ topology. The selection depended on application priorities, particularly THD. The conventional 2L VSI was competitive in mass and volume, but its high voltage THD (76%) penalised efficiency by requiring high switching frequencies to meet low current THD. In contrast, the 3L VSI had 39% voltage THD, offering a superior trade-off by meeting THD limits at lower, more efficient switching frequencies. In particular, the T- type had the most balanced performance for this application. Interleaved VSIs consistently underperformed, as the mass, volume, and loss penalties of their interphase inductors outweighed any system-level filtering benefits.
This framework provides a reproducible method for quantitative topology benchmark- ing, highlighting non-obvious trade-offs and guiding aerospace inverter design.