Insulation and Switching Performance Optimization for Partial-Discharge-Free Laminated Busbar in More-Electric Aircraft Applications

This article proposes an insulation design strategy of laminated busbar to avoid partial discharge (PD) in more-electric aircraft (MEA) applications. During high-altitude operation, the converters for MEA are exposed to low air pressure, making partial discharge being triggered easier. But blindly increasing the insulation results in excessive parasitic inductance and degraded switching performance, which lead to serve losses and electromagnetic interference (EMI) problems during high-frequency switching operations. This article targets this issue and conducts a systematic study for laminated busbars in these high-density converters for MEA application. Moreover, it proposes a model-based codesign strategy to simultaneously optimize the busbar's stray inductance control and insulation layer design. To verify the design strategy, a busbar for a three-level (3L) 450-kVA converter is designed, fabricated, and evaluated. The measured minimum partial-discharge inception voltage is 43% higher than the rated voltage at 0.2 atm. Moreover, busbar stray inductance of 12.0 nH is achieved, which is lower than published literature for 3L converters. The low-inductance busbar can fully exploit the advantage of SiC-mosfet, helping it reduce switching loss by 66.7% at 1 kV 350 A with minimum voltage overshoots.