A Low Inductance, High Power Density 3L-TNPC Power Module for More-electric Aircraft Applications

Three-level T-type neutral-point-clamped converters (3L-TNPCs) are widely used in propulsion converters in more-electric aircraft (MEA) applications as higher efficiency, improved output total harmonic distortion (THD), and lower common-mode noise. However, such topology suffers from high stray inductance because of complicated power loop. Its power module current density is also less than the two-level (2L) converter as the increased switch counts. To solve the issue, this article proposes a novel hybrid-structure-based full SiC-MOSFET 3L-TNPC power module. The module has a printed circuit board (PCB) stacked on top of the substrate, with bare dies soldered on direct bond copper (DBC) and connected to PCB by bonding wires. Such a structure allows the power loop on both the substrate and PCB. This reduces the stray inductance by enhanced mutual inductance cancellation. The heat from dies can be directly dissipated through the substrate and the proposed base-plate-embedded cooling system, enhancing thermal conductivity by 55%. Based on the structure, a 1.2-kV, 300-A 3L-TNPC module is fabricated with a stray inductance of 2.5 nH. Because the stray inductance is 68% smaller than a state-of-the-art module, faster driving speeds can be used with limited voltage overshoots. As a result, the switching loss of the module is reduced by 62.5% compared with the same bare die at a state-of-the-art module’s power loop at 800 V, 450 A. Eventually, impedance characterization by impedance analyzer, double-pulse tests, and continuous tests are performed for experiment evaluation.