Application thermal research of forced-air cooling system in high-power NPC three-level inverter based on power module block

During the process of cooling system design, the traditional method is calculating power losses of power devices, building thermal model of power devices, establishing system structure model, and making thermal analysis. While, the ideal assumptions and complex equivalent models in traditional methods bring in large error and the analysis of whole system model reduces the effectiveness of cooling system design for complicated high-power inverters. In this paper, the power losses of power devices in NPC (Neutral-Point-Clamped) three-level inverter based on SVPWM(Space Vector Pulse Width Modulation) was calculated firstly; the input power and cooling power of each power module block were analyzed, and the cooling power of each block supplied by cooling fan was obtained to figure out the cooling fan parameters. The designed forced-air cooling system was proved by finite element simulation. Finally, the temperature rise experiment was carried out on a 1 MW NPC three-level inverter, and the results proved the effectiveness and feasibility of the proposed method.