Air-Cooling System Optimization for IGBT Modules in MMC Using Embedded O-Shaped Heat Pipes
Binyu Wang, Laili Wang, Fengtao Yang, Wei Mu, Mengjie Qin, Fan Zhang, Dingkun Ma, Jianpeng Wang, Jinjun Liu
Abstract
Insulated gate bipolar transistor (IGBT) modules are the most critical components of modular multilevel converters (MMCs). However, they are subjected to repetitive thermo-mechanical stress caused by thermal cycles on different materials, which can easily lead to failures in the solder layers. Moreover, when MMCs work at high power factor, the IGBT modules have severely uneven temperature distribution due to the inherent dc-bias in arm currents. Some chips are much hotter than others. These hot spots significantly reduce the lifetime of the whole module. This article proposes an optimized and low-cost air-cooling system dedicated to the application of MMC. Uniquely designed O-shaped heat pipes are embedded on the heatsink to add another thermal path without extra fans and fins. The unique shape and layout of heat pipes can minimize the hot spots temperature. The operating principle and power loss of MMC are analyzed first. Then, 3-D finite element (FE) simulation is performed in ANSYS 19.2. Nine modified air-cooling heatsinks with embedded heat pipes are proposed and compared. Finally, the optimal one and a conventional air-cooling heatsink are fabricated for experimental evaluation. The comparative experiment results show that the optimized cooling system is superior over the conventional one by 20% lower in the hot spot temperature.